GB2512149A

GB2512149A - Control System

Info

Publication number: GB2512149A
Application number: GB1310872.5A
Authority: GB
Inventors: Philip John Rimmer; Michael William Smith
Original assignee: ISOTERA Ltd
Current assignee: ISOTERA Ltd
Priority date: 2013-06-18
Filing date: 2013-06-18
Publication date: 2014-09-24
Anticipated expiration: 2033-06-18
Also published as: GB2512149B; GB201310872D0; WO2014203186A3; WO2014203186A2

Abstract

A system 100 for controlling a plurality of electrical devices 21, particularly luminaires e.g. including one or more light-emitting diode (LED) lamps, comprises at least one zone 21, 22, each zone having a bus 401, 402, at least one command provider 30 connected to the bus and configured to provide a command signal thereto in response to an action, a controller 101, 102, connected to the bus and configured to receive command signals therefrom and to provide an analogue control signal thereto dependent upon the command signals, and at least one driver 20 connected to the bus and configured to receive the control signal therefrom, and associated with at least one of the plurality of electrical devices and configured to control operation thereof in dependence upon the control signal.

Description

tM:;: INTELLECTUAL .*.. PROPERTY OFFICE Application No. 0B1310872.5 RTM DateS August2013 The following terms are registered trade marks and should be read as such wherever they occur in this document: Bluetooth Intellectual Properly Office is an operaling name of Ihe Patent Office www.ipo.gov.uk Control system

Field

The present invention relates to a system for controlling operation of a plurality of electrical devices, particularly luminaires.

Background

Various systems for controlling lighting are known. Many of these, for example the system described in EP 2443854 Al, involve digital communications between a plurality of data processing apparatuses.

S urn mary According to a first aspect of the present invention, there is provided a system suitable for controlling operation of a plurality of electrical devices, particularly luminaires. The system comprises: at least one zone comprising: a bus; at least one command provider connected to the bus and configured to provide a command signal thereto in response to an action; a controller connected to the bus and configured to receive command signals therefrom and to provide an analogue control signal thereto dependent upon the command signals; and at least one driver connected to the bus and configured to receive the control signal therefrom, and associated with at least one of the plurality of electrical devices and configured to control operation thereof in dependence upon the control signal.

Thus, the system can be lower cost and easier to install and maintain than many lighting control systems (e.g. those involve digital communications between a plurality of data processing apparatuses).

The at least one command provider, the controller and the at least one driver may be devices which are remote from one another.

The system may comprise a plurality of zones, wherein each of the plurality of zones comprises a plurality of drivers associated with a plurality of electrical devices, and wherein electric devices associated with the same zone are caused to operate in the same way.

At least one driver may be configured to control the power used by the associated at least one electrical device, and the power may be a function of the level of the control signal.

The system may comprise first and second zones, wherein the controller of the second zone is connected to the bus of the first zone and configured to receive the control signal therefrom, and wherein the control signal provided to the bus of the second zone is dependent upon the control signal received from the bus of first zone. The control signal provided to the bus of the second zone may be determined in such a way that it is either no larger than or no smaller than the control signal received from the bus of the first zone. The system may comprise a tree network of zones comprising a zone of a first type and a plurality of zones of a second type, wherein the controller in each zone of the second type is connected to the bus of another zone in the tree network and is configured to receive the control signal therefrom, and wherein the control signal provided to the bus of each zone of the second type is dependent upon the control signal on the bus of the zone of the first type.

The system may comprise first and second zones, wherein the controller of the second zone is connected to the bus of the first zone and configured to provide command signals thereto.

The bus may comprise a conductor for carrying the command signal and another conductor for carrying the control signal.

At least one zone may comprise a plurality of command providers connected to a conductor comprised in the bus. At least one zone may comprise a plurality of drivers connected to a conductor comprised in the bus. Only one controller may be connected to the bus.

Communications between the at least one command provider and the controller, and between the controller and the at least one driver may be simplex.

The system may comprise first and second zones, wherein signals on the bus of the first zone are not provided to the bus of the second zone and vice versa.

The bus may comprise a first conductor for carrying the command signals, wherein the first conductor is loosely held at a first voltage; and at least one command provider may be configured to set the first conductor to a voltage different from the first voltage in response to the action, thereby providing a command signal. The controller may be configured to loosely hold the first conductor at the first voltage. The command signal may correspond to a voltage pulse. At least one command provider may comprise a switch configured to connect the first conductor to a voltage reference to provide a command signal. At least one of a first type of command provider may comprise a switch configured to connect the first conductor to a first voltage reference via a path with a first impedance to provide a first type of command signal; at least one of a second type of command provider may comprise a switch configured to connect the first conductor to a second voltage reference via a path with a second impedance to provide a second type of command signal; and the first impedance may be less than the second impedance, such that the first type of command signal has priority over the second type of command signal. The bus may further comprise a second conductor, wherein the second conductor is grounded; and at least one of a first type of command provider may comprise a switch configured to connect the first and second conductors to provide a command signal. At least one of the first type of command providers may comprise a further switch configured to provide a further command signal at a voltage between the first voltage and ground.

The system may comprise at least one of a first type of command provider configured to provide a first type of command signal and at least one of a second type of command provider configured to provide a second type of command signal different from the first type of command signal; and the controller may be configured to provide a control signal differently dependent upon the first and second types of command signals.

The system may comprise at least one of a first type of command provider comprising a user interface and configured to provide a command signal of a first type in response to a user input; and the controller may be configured to change the control signal from a first level to a second level different from the first level in response to receiving a command signal of the first type. The first and second levels may be comprised in a sequence of levels. The at least one driver may be configured to switch on the associated at least one electrical device when the control signal changes from the first level to the second level, and may be configured to switch off the associated at least one electrical device when the control signal changes from the second level to the first level.

The system may comprise at least one of a second type of command provider comprising a sensor and configured to provide a command signal of a second type in response to a detection event; the controller may be configured to change the control signal from a first level to a second level different from the first level in response to receiving a command signal of the second type; and the at least one driver may be configured to switch on the associated at least one electrical device when the control signal changes from the first level to the second level. The system may comprise at least one of a second type of command provider comprising a sensor and configured to provide a command signal of a second type in response to a detection event; the controller may be configured to change the control signal from a second level to a first level different from the first level in response to determining that the time elapsed since a command signal of the second type or of another type was last received is equal to or greater than a predetermined time; and the at least one driver may be configured to switch off the associated at least one electrical device when the control signal changes from the second level to the first level. The second type of command provider may comprise a presence detector.

At least one driver may be configured to provide power to the bus, wherein the power is obtained from power provided by a power line) wherein the power line is for distributing power to the plurality of electrical devices; and the controller and/or at least one command provider may be configured to obtain power from the bus.

The system may comprise first and second zones, wherein the controller of the second zone is connected to the bus of the first zone and corresponds to a command provider comprised in the first zone.

The controller of at least one zone may be configured to receive internal signals from apparatus associated with the controller and to provide an analogue control signal to the bus dependent upon the internal signals. The controller of at least one zone may be configured to receive internal signals from apparatus associated with the controller, may be connected to the bus of another zone, and may be configured to provide command signals thereto dependent upon the internal signals. The apparatus may comprise a user interface, a detector, and/or a communications interface for communicating with a remote device.

S

The controller may have a plurality of operating modes corresponding to a plurality of ways in which the analogue control signal is provided dependent upon received signals.

The system may comprise at least one other zone comprising another controller in place of the controller, the other controller configured to provide the control signal to the bus in the other zone independently of any command signals. The other controller may be configured to provide the control signal using power obtained from the bus.

The system may comprise first and second zones; the second zone may comprise a controller comprising a light sensor configured to sense a light level; and the controller comprising the light sensor may be connected to the bus of the first zone and configured to obtain the control signal therefrom, and may be connected to the bus of the second zone and configured to provide a control signal thereto which is dependent upon the control signal received from the bus of the first zone and/or upon the light level. The control signal provided to the bus of the second zone may be reduced dependent upon the light level. The control signal provided to the bus of the second zone may correspond to a predetermined level when the light level is less than or equal to a predetermined level, and otherwise may correspond to the control signal received from the bus of the first zone.

The system may comprise a power supply for supplying power via a power line to the plurality of electrical devices and may comprise an additional bus. At least one command provider and/or the controller of at least one zone may be connected to the additional bus and is configured to provide an off signal thereto in response to an action; the power supply may be connected to the additional bus and may be configured to receive the off signal therefrom and, in response thereto, to provide a further off signal via the power line to the at least one driver; and the at least one driver may be configured to received the further off signal and, in response thereto, to switch off the associated at least one electrical device. The system may comprise an additional bus connected to the bus of at least one zone. At least one command provider and/or the controller of at least one zone and/or a power supply for supplying power to the plurality of electrical devices may be connected to the additional bus and may be configured to provide an off signal thereto in response to an action, wherein providing the off signal comprises grounding a conductor included in the additional bus; the bus may include a conductor for carrying the control signal; and the additional bus may be connected to the bus such that, when the conductor in the additional bus is grounded, so too is the conductor for carrying the control signal, thereby causing the at least one driver to switch off the associated at least one electrical device. At least one command provider, the controller of at least one zone and/or the power supply may be configured to provide an additional command signal to the additional bus in response to an action; and the controller of the at least one zone and/or the power supply may be configured to receive the additional command signal from the additional bus and, in response thereto, to cause at least one of the plurality of electrical devices to switch off.

The bus of at least one zone may be divided into two or more separate parts, wherein each part is connected to a power line communication device, wherein each power line communication devices is also connectable to a power line for distributing power to the plurality of electrical devices. The system may comprise first and second zones, wherein the bus of each of the first and second zones is divided into two or more parts, wherein each part of the bus of the first zone is connected to a power line communication device configured to communicate via a first channel of the power line, and wherein each part of the bus of the second zone is connected to a power line communication device configured to communicate via a second channel of the power line.

The system may comprise: at least one power line communication device of a first type connected to a bus and connectable to a power line, wherein the power line is for distributing power to the plurality of electrical devices; and a power line communication device of a second type connectable to the power line and configured to send and/or receive command signals and/or control signals to and/or from the bus via the at least one power line communication device of the first type.

The system may comprise at least one device connected to a bus and connectable to a power line, wherein the power line for distributing power to the plurality of electrical devices, wherein the device is configured to obtain power from the power line and provide the power to the bus for powering devices connected thereto.

At least one command provider maybe configured to provide a command signal of another type to the bus in response to another action; and the controller of at least one zone may be configured: to provide the control signal independently of the command signal of the other type; and, in response to receiving the command signal of the other type, to provide an indication thereof and/or to provide a command signal of the other type to a bus of another zone to which the controller is connected. The other action may include determining that an error has occurred.

The system may comprise at least one other zone without any command providers, without any controllers and/or without any drivers.

The system may comprise at least one command provider configured to receive a command signal from the bus and, in response thereto, to provide an indication thereof and/or to temporarily refrain from sending a command signal in response to an action.

According to a second aspect of the present invention, there is provided a kit of parts for assembly into the system. The kit comprises at least one command provider, the controller and at least one driver. The kit may comprise a plurality of cable sections and at least one tee connector for assembly into the bus, wherein each of the plurality of cable sections is connectable to the tee connector, the command provider, the controller and the driver.

According to a third aspect of the present invention, there is provided a controller suitable for use as part of the system. The controller comprises: a first connector for connecting to a first bus and a second connector for connecting to a second bus. The controller is configured to: receive command signals from the first bus via the first connector, wherein the command signals are provided to the first bus by at least one command provider in response to action; receive a second analogue control signal from the second bus via the second connector, wherein the second control signal is provided to the second bus by another controller; and provide a first analogue control signal to the first bus via the first connector dependent upon the command signals and/or the second control signal.

There may be provided a command provider, controller or driver as specified above.

Brief Description of the Drawings

Certain embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 illustrates a system for controlling lighting; Figure 2 illustrates part of a bus which is part of the system of Figure 1; Figure 3 illustrates a controller which is part of the system of Figure 1; Figure 4 illustrates another controller which is part of the system of Figure 1; Figure 5 illustrates a command provider which is part of the system of Figure 1; Figure 6 illustrates part of another system for controlling lighting; Figure 7 illustrates a command provider corresponding to a switch/dimmer) which is part of the system of Figure 6; FigureS illustrates a command provider corresponding to a presence detector which is part of the system of Figure 6; FigureS illustrates example signals in buses which are part of the system of FigureS; Figure 10 illustrates another controller which may be used in the system of Figure 6; Figure 11 illustrates another controller which maybe used in the system of Figure 6; Figure 12 illustrates another system for controlling lighting; Figure 13 illustrates another controller which is part of the system of Figure 12; Figure 14 illustrates a part of another system for controlling lighting; Figure 15 illustrates another system for controlling lighting; Figure 16 illustrates another system for controlling lighting; Figure 17 illustrates another controller; Figure 18 illustrates a power-line-communication device; and Figure 19 illustrates a power harvester.

Detailed Description of the Certain Embodiments

First system 100 Referring to Figure 1, a first system 100 for controlling lighting will be described. The first system 100 is divided into a first zone 2 and a second zone 22. However, there may be any number of one or more zones 2. The first zone 2 includes a first controller 101 and the second zone 22 includes a second controller 102. The first zone 2 includes first, second and third drivers 20k, 202, 203, and the second zone 2 includes fourth and fifth drivers 204, 20.

However, there may be no drivers 20 or any number of one or more drivers 20 in each zone 2.

The first, second, third, fourth and fifth drivers 2O, 202, 203, 204, 205 are included in first, second, third, fourth and fifth luminaires 2l, 212, 213, 214, 21 respectively. Each luminaire 21 includes one or more light-emitting diode (LED) lamps (not shown). Power is distributed to the luminaires 2l, 212, 213, 214, 21 by a power distribution system (not shown), such as is described in WO 2010/106375 A2. The same power supply is preferably used for all of the luminaires 21, 212, 213, 214, 21. The first zone 21includesfirstand second command providers 302, and the second zone 2 includes a third command provider 303 However, there may be no command providers 30 or there may be any number of one or more command providers 30 in each zone 2. Controllers 10, drivers 20 and command providers 30, are collectively referred to hereinafter as system devices'. A first bus °1 interconnects the system devices within the first zone 2. A second bus 402 interconnects the system devices within the second zone 22. The second controller 102 is also connected to the first bus 402.

As will be explained in more detail below, within each zone 2, each command provider 20 provides a command signal to the bus 40 in response to an action, the controller 30 receives command signals from the bus 40 and provides an analogue control signal to the bus 40 dependent upon the received command signals, and each driver 20 receives the control signal from the bus 40 and controls the power and hence brightness of the one or more LED lamps in the luminaire 21 in dependence upon the received control signal. Accordingly, the brightness of the LED lamps is the same within each zone 2. Furthermore, a controller 10 of a zone 2 that is also connected to another zone 2 may be configured to provide a control signal to the zone 2 that is dependent upon the control signal in the other zone 2. A zone 2 in which the control signal is dependent upon the control signal in another zone is referred to hereinafter as a dependent zone'. A controller 10 of a zone 2 that is also connected to another zone 2 may also be configured to provide command signals to the other zone 2.

The first bus 40 includes eleven cable sections 42 42 and five tee connectors 445, and the second bus °2 includes six cable sections 42 42 and two tee connectors 44, However, each bus 40 may include any number of one or more cable sections 42 and may include no tee connectors 44 or any number of one or more tee connectors 44.

The first controller 101 is connected via a first type of connector 46' to a first cable section 42k.

The first type of connector 46' is referred to hereinafter as a blue connector'. The first cable section 42 is also connected to a first tee connector which is also connected, via a second cable section 422, to the first driver 20 and, via a third cable section 423, to a second tee connector The second tee connector is also connected, via a fourth cable section 424, to the second driver 202 and, via a fifth cable section 42 to a third tee connector 443. The third tee connector 443 is also connected, via a sixth cable section 42, to the third driver 203 and, via a seventh cable section 427, to a fourth tee connector 444. The fourth tee connector 444 is also connected, via an eighth cable section 42, to the first command provider and, via a ninth cable section 42, to a fifth tee connector 44. The fifth tee connector 445 is also connected, via a tenth cable section 4210, to the second command provider 302 and, via an eleventh cable section 4211 to the second controller 102. The connection to each of the first and second command providers 301, 3O2and to the second controller 102 is via a second type of connector 46", which will be referred to hereinafter as a red connector' 46". The second controller 102 is connected via a blue connector 46' to a twelfth cable section 4212. The twelfth cable section 4212 is also connected to a sixth tee connector 445 which is also connected, via a thirteenth cable section 4213 and a red connector 46", to the third command provider 303 and, via a fourteenth cable section 4214 to a seventh tee connector 447. The seventh tee connector 447 is also connected, via a fifteenth cable section 4214, to the fourth driver 204 and, via a / a sixteenth cable section 4216 to the fifth driver 20.

In other examples, the cable sections 42, tee connectors 44 and connectors 46 may be different. For example, system devices may have integral cable sections 42 (flying leads), tee connector 44 may be connected directly to system devices, tee connectors 4d may be included in system devices, and/or two or more cable sections 42 may be interconnected, e.g. using one or more suitable interconnectors.

The system devices may be connected to one another in different arrangements. In particular, the system devices within a zone 2 may be connected to each other in any sequence. Furthermore, the system device within a zone 2 need not be connected to each other in a single line as in the figure. There may be two or more lines of system devices, and each line of system devices may be connected to any point of any other line of system devices, for example by way of a tee connector 44. A controller 10 (e.g. the second controller 102) may be connected via its red connector 46' to any point in another zone (e.g. the first zone 21), for example by way of a tee connector 44.

Only one blue connector 46' is generally connected to each bus 40. No red connectors 46" or any number of one or more red connectors 46" can be connected to each bus 40.

Referring to Figure 2, the cable sections 42, tee connectors 44 and connectors 46 will now be described in more detail. Each cable section 42 includes four conductors (hereinafter referred to as lines'), i.e. a ground line 42a, a control line 42b, a command line 42c and a power line 42d. The cable section 42 has connectors 46 at each end. Each tee connector 44 has three connectors 46. Each system device has at least one connector 46 (for example, the second controller 102 includes two connectors, a blue connector 46' and a red connector 46"). Each connector 46 includes a ground-line contact 46a, a control-line contact 46b, a command-line contact 46c and a power-line contact 46d (although one or more contacts 46a, 46b, 46c, 46d need not be included in some cases). In the tee connector 44, corresponding contacts 46a, 46b, 46c 46d are interconnected, thereby interconnecting corresponding lines 42a, 42b, 42c, 42d of cable sections 42 connected to the tee connector 44. Accordingly) each bus 40 includes one or more interconnected ground lines 42a (hereinafter referred to as the ground line 40a of the bus 40), one or more interconnected control lines 42b (hereinafter referred to as the control line 40b of the bus 40), one or more interconnected command lines 42c (hereinafter referred to as the command line 40c of the bus 40) and one or more interconnected power lines 42d (hereinafter referred to as the power line 40d of the bus 40).

As will be explained in more detail below, the control line 40b of a bus 40 has a voltage level that is set by the controller 10 that is connected to the bus 40 via a blue connector 46'. In this example, the level can vary continuously between 0 and 10 volts. However, the level could vary between several discrete levels and/or in a different voltage range. The command line 40c of a bus 40 has a voltage level that is loosely held by the controller 10 at 2.5 volts and can also be set high' (5 volts) or low' (0 volts) or semi-low' (1.2 volts) by each command provider 30 connected to the bus 40. In other examples, there could be a different number of two or more voltage levels of the command line 40c. Command providers 30 generate voltage pulses on the command line 40c of the bus 40. However, this need not be the case. The power line 40d of a bus 40 is at nominally 6 volts and is for transmitting power, for example, from drivers 20 connected to the bus 40 to controllers 10 and command providers 30 connected to the bus 40. The ground line 40a of a bus 40 defines 0 volts. The ground line 40a and power line 40d of one bus 40 may be connected to corresponding lines 40a, 40d of another bus 40 in a controller 10 (e.g. the second controller 102).

In this example, the cable sections 42, tee connectors 44 and connectors 46 are of a registered jack Rill type. However, different types of cable sections 42, tee connectors 44 and/or connectors 46 may be used.

Referring to Figure 3, the first controller l0 will now be described in more detail. The first controller 10 includes a microprocessor lOa, an interface lob and a blue connector 46'. The microcontroller lOa and the interface lob are operatively connected to each other. The interface lob is also connected to each of the ground-line contact 46a, the control-line contact 46b, the command-line contact 46c and the power-line contact 46d of the blue connector 46'. The microcontroller lOa includes at least one processor lOc and memory lOd.

The processor lOc executes computer-readable instructions) e.g. one or more computer programs, stored in the memory lOd and/or in other storage (not shown). This causes the first controller lO to perform operations described herein. The computer-readable instructions may be updatable, by any suitable means. The first controller 101 includes a voltage regulator (not shown). The power line contact 46d of the blue connector 46' is connected to an input to the voltage regulator. The voltage regulator provides an output that is maintained at 5 volts and is used to power components of the first controller 10k. In other examples, the first controller 10 need not include a voltage regulator. The first controller 101 loosely holds the voltage of the command line 40b of the first bus 40 at 2.5 volts. In this example, the output from the voltage regulator is connected to the ground-line contact 46a of the blue connector 46' via a voltage divider including two equal resistors, e.g. 10 kiloohm resistors, and the output of the voltage divider is connected to the command-line contact 46c of the blue connector 46'. However, this may be done in a different way.

The first controller 101 senses changes in the voltage of the command line 40c of the first bus 40, i.e. receives command signals, and sets the voltage level of the control line 40b of the first bus i.e. provides a control signal, in dependence upon the received command signals. To determine the command signal, the voltage level of the command line 40c is compared with various thresholds (e.g. less than 0.5 volts (low), between 0.5 and 2 volts (semi-low), etc.).

The period of time during which the voltage level is in one of the ranges defined by the thresholds may also be determined. The dependence of the control signal jupon the received command signals can take any suitable form. In some examples, the first controller 101 may include additional circuitry (not shown) to provide signals (hereinafter referred to as internal signals') other than command signals to the microprocessor ba. For example, the first controller 10 may include a user interface, a sensor and/or a communications interface. The control signal may also depend upon the internal signals. Where different command signals and/or internal signals are received which would otherwise lead to different control signal being provided, priority may be given to the signal which last changed and this signal may be used to determine the control signal provided. The dependence of the control signal on the received command signals and/or the internal signals may be pre-set and/or set by a user.

Furthermore, the first controller lOi may operate in one of two or more modes, each of which may correspond to a different dependence. Modes may be selected by a user in any suitable way.

Referring to Figure 4, the second controller 102 will now be described in more detail. The second controller 102 includes a microprocessor ba, an interface lob') a blue connector 46' and a red connector 46". The microcontroller bOa and the interface lob' are operatively connected to each other. The interface bob' is also connected to each of the ground-line contact 46a, the control-line contacts 46b, the command-line contacts 46c and the power-line contact 46d of the blue connector 46' and the red connector 46". The microcontroller ba includes at least one processor bc and memory bOd. The processor bc executes computer-readable instructions, e.g. one or more computer programs, stored in the memory lod and/or in other storage (not shown). This causes the second controller 102 to perform operations described herein. The computer-readable instructions may be updatable, by any suitable means. The second controller 102 includes a voltage regulator (not shown). The power line contact 46d of the blue connector 46' is connected to an input to the voltage regulator. The voltage regulator provides an output that is maintained at 5 volts and is used to power components of the second controller 102. In other examples, second controller 102 need not include a voltage regulator. The second controller 102 loosely holds the voltage of the command line 40b of the second bus 402 at 2.5 volts. In this example, the output from the voltage regulator is connected to the ground-line contact 46a of the blue connector 46' via a voltage divider including two equal resistors) e.g. 10 kiloohm resistors, and the output of the voltage divider is connected to the command-line contact 46c of the blue connector 46'.

However, this may be done in a different way. The power-line contacts 46d of the blue and red connectors 46', 46" are interconnected and so power can be transferred between the first and second zones 2, 22. The ground-line contacts 46a of the blue and red connectors 46', 46" are also interconnected.

The second controller 102 receives command signals and/or internal signals as described above in relation to the first controller 101, and provides a control signal dependent upon the received command signals and/or the internal signals. The command signals are received and the control signal is provided via the blue connector 46'. The second controller 102 also receives a control signal from the first bus °1 via the red connector 46" and sets the control signal provided to the second bus 402 via the blue connector 46' in dependence upon the received control signal. Where different command signals, internal signals and/or control signals are received which would otherwise lead to a different control signal being provided, priority may be given to the signal which last changed and this signal may be used to determine the control signal provided. In some examples, the second controller 102 may also provide command signals to the first bus 40 via the red connector 46". The provided command signals are dependent upon the received command signals and/or the internal signals. Accordingly) in some instances, the second controller 102 can function as a command provider 30. The dependence of the control signal and/or the provided command signals on the received command signals and/or the internal signals may be pre-set and/or set by a user.

Furthermore, the second controller 102 may operate in one of two or more modes, each of which may correspond to a different dependence. Modes may be selected by a user in any

suitable way.

The drivers 20 will now be described in more detail. Each driver 20 senses the level of the control line 40b of the bus 40 to which it is connected, i.e. receives the control signal. The driver 20 controls the power drawn by the one or more LED lamps in the luminaire 21 in dependence upon the level of the control signal. The driver may do this in any suitable way.

For example, the driver 20 may include a suitable power regulator, e.g. a current regulator. In this example, the driver 20 power drawn varies between 0 and 100% of a certain maximum power as a linear function of the level of the control signal. However, the function may be different. For example, the power may be zero for control signals below a first threshold level (e.g. 0.5 volt). The power may be equal to a predetermined minimum power level (e.g. 10% of the maximum power) for control signals between the first threshold level and a second threshold level (e.g. 1 volt). In this way, the LED lamps can be switched off and/or set to a low level more easily. The driver 20 also transfers power, e.g. a current of 20 milliamperes, to the power line 40d of the bus 40 to which it is connected. The power transferred is taken from the power provided to the LED lamps. The driver 20 also transfers a small current, e.g. 200 microamperes, to the control line 40b of the bus 40 to which it is connected. This current has the tendency to increase the voltage level of the control line 40b. Thus, if a controller lOis not connected to the bus 40, then the level of the control line 40b increases to a level above 10 volts and the driver 20 sets the power drawn by the LED lamps to the maximum power.

Referring to Figures, the command providers 3Owill now be described in more detail. Each command provider 30 includes command-providing circuitry 30a and a red connector 46". In this example, the command-providing circuitry 30a is connected to the ground-line contact 46a, the command-line contact 46c and the power-line contact 46d of the red connector 46".

However, the command-providing circuitry 30a need not be connected to one or both of the ground-line contact 46a and power-line contact 46d, and may be connected to the control-line contact 46d. The command-providing circuitry 30a is configured to provide a command signal by setting the level of the command line 40c of a bus 40 to a particular level, e.g. high (5 volts) or low (0 volts) or semi-low (1.2 volts), in response to an event at the command provider 30k.

The level may be set for a particular period of time. The command-providing circuitry 30a may include a user interface, a sensor and/or a communications interface, and the event may include, for example, a user interacting with the user interface (e.g. a switch), an event being detector by the sensor (e.g. a presence detector) or a signal from a remote device (e.g. a remote controller) being received by the communication interface.

A command provider 30 may also be configured to provide a command signal of another type, i.e. a type that is not used by a controller 10 to determine a control signal. These command signals may be for another purpose, e.g. reporting of an event such as an error at the command provider 30. A controller 10 may respond by providing an indication of the event, e.g. via a user interface and/or via a communications interface. Alternatively or additionally, the controller 10 may comprise the same features as the second controller 102 and may be configured to respond by providing a command signal of the other type via the red connector 46" to another zone 2. In this way, another controller 10 can provide the indication of the event. Any appropriate action can then be taken, e.g. controllers lOin the system can be inspected to identify the zone 2 in which the event has occurred. The command signal of the other type may include, for example, repeated high-voltage pulses, each of which may have a different, e.g. smaller, width to those provided by any other system devices. The repetition can mean that command signals of the other type are unlikely to be masked by any other command signals. Moreover, the smaller pulse width can mean that the command signals of the other type are unlikely to affect operation of controllers 10 that are not configured to receive command signals of the other type and only receive command signals corresponding to longer pulses.

Second system 200 Referring to Figure 6, a part of a second system 200 will now be described. The second system includes a third zone 23 including a third controller 103, sixth, seventh and eighth drivers 20, 207, 20 included in sixth, seventh and eighth luminaires 21, 217, 21 respectively, and fourth and fifth command providers 304, 30g. The drivers 205, 207, 2O and the luminaires 215, 217, 21 are the same way as those in the first system 100. The system devices within the third zone 23 are interconnected by a third bus 403. The third controller 103 is connected via a blue connector 46' to the third bus 403, and is also connected via a red connector 46" to a fourth bus 404 of a fourth zone 24.

Referring to Figure 7, the fourth command provider 304 will now be described in more detail.

The fourth command provider 304 corresponds to a switch/dimmer. The fourth command provider 304 includes command-providing circuitry 30a' and a red connector 46". The command-providing circuitry 30a' is connected to the ground-line contact 40a and the command-line 40c contact 40 of the red connector 46". The command-providing circuitry 30a' includes a first switch 32 connected between the ground-line contact 40a and the command-line 40c contact. The command-providing circuitry 30a' includes a second switch 322 connected in series with first and second diodes between the ground-line contact 40a and the command-line 40c contact. The first and second switches 32k, 322 are normally-open switches. When the first switch 32 is closed, the fourth command provider 304 sets the level of the command line 40c of the third bus 403 to a low level, i.e. 0 volts. When the second switch 322 is closed, the fourth command provider 304 sets the level of the command line 40c of the third bus 403 to a semi-low level, i.e. 1.2 volts. In this example, the first and second switches 32, 322 are mechanical switches associated with a movable element (e.g. a rocker) that allows a user to close the first switch 32 or the second switch 32. The first switch 32 or the second switch 32 is closed for a period of time which depends upon how the user operates the movable element. Accordingly, the fourth command provider 304 provides command signals in the form of voltage pulses with variable widths. In other examples, the first and second switches 32 may be controlled in a different way, the first and second switches 32, 322 may be electronic switches, and/or the voltage pulses may have one or more predetermined widths. In some examples, the fourth command provider 304 may include a communications interface (not shown) for communicating with a remote device and for enabling the remote device to operate the first and second switches 32k, 322. In some examples, the fourth command provider 304 may draw power from the power line 40d of the third bus 403. In some examples, the fourth command provider 304 need not include the second switch 322 and the diodes 33k, 333* Referring to Figure 8, the fifth command provider 305 will now be described in more detail.

The fifth command provider 30 corresponds to a presence detector. The fifth command provider 30 includes command-providing circuitry 30a" and a red connector 46". The command-providing circuitry 30a" includes a passive infrared (PIR) motion detector 34.

However, the command-providing circuitry 30a" may include a different type of presence detector. The command-providing circuitry 30a" is connected to the ground-line contact 46a, the command-line 46c contact and the power-line contact 46d of the red connector 46". The fifth command provider 30 includes a voltage regulator 35. The power line contact 46d of the blue connector 46' is connected to an input to the voltage regulator 35. The voltage regulator 35 provides an output that is maintained at 5 volts and is used to power the components of the fifth command provider 305, e.g. the motion detector 34. In other examples, the fifth command provider 30 need not include a voltage regulator. The motion detector 34 outputs a signal in response to detecting motion. The command-providing circuitry 30a" includes a switch 36. One end of the switch 36 is connected via a resistor 37 to the output of the voltage regulator. The other end of the switch 36 is connected to the command-line contact 46c of the red connector 46". The switch 36 is an electronic switch. The motion detector 34 is operatively connected to the switch 36. When motion is detected, the switch 36 momentarily closes and generates a high voltage (5 volts) pulse on the command line 40c of the third bus 403. In this example, each pulse has a predetermined width of 100 milliseconds. However) each pulse may have a different width. The resistor 37 has a relatively high impedance of e.g. 2.2 kiloohms. Accordingly, if the switch 36 is closed at the same time as one of the switches 32k, 322 in the fourth command provider 304 (Figure 7), which have a relatively low impedance path to ground, then the level of the command line 40c of the third bus will be low. Furthermore, the resistor 37 also limits the current provided to the command line 40c from the fifth command provider 30, e.g. to 1 milliampere. In other examples, the fifth command provider 30 may include a different means of limiting the current provided to the command line 40c.

The third controller 103 comprises the same features as the second controller 102 (Figure 4).

In this example) the third controller 103 is configured to provide a control signal which depends upon low or semi-low-voltage pulses received on the command line 40c of the third bus 403, i.e. from the fourth command provider 304 (switch/dimmer). In response to receiving a low-voltage pulse of a particular width) the third controller 103 changes the control signal from a current level to a next level in a sequence of levels. In response to receiving a semi-low-voltage pulse of a particular width, the third controller 103 changes the control signal from a current level to a previous level in a sequence of levels. The sequence of levels may) for example, consist of five levels) i.e. 0, 2.5)5,7.5 and 10 volts. Where the pulses are longer than a particular width, then the third controller 103 may change the control signal by two or more levels depending upon the width of the pulse and/or may smoothly increase or decrease the control signal during the pulse. Accordingly, a user can use the fourth command provider 304 to change the brightness of the LED lamps in the third zone 23 between 0 and 100% in various different ways. In other examples, the sequence of levels may consist of a different sequence of two or more levels, and/or the fourth command provider 304 may respond to the pulses in different ways. For example, the sequence of levels may consist of only two levels, i.e. 0 and 10 volts. The sequence of levels is stored in the memory lOd. After initialisation, or after another event (e.g. an event which results in the control signal being set toO volts), the third controller 103 may revert to a default one of the sequence of levels, e.g. the first level.

Furthermore, the third controller 103 is configured to provide a control signal which also depends upon high-voltage pulses received via the command line 40c of the third bus 403, i.e. from the fifth command provider 30 (presence detector). The third controller 103 may operate in one of several presence-detection modes. For example, in a first presence-detection mode (hereinafter referred to as an manual on/auto off mode'), the third controller 103 monitors the time elapsed since the last high or (semi-)low voltage pulse on the command line 40c, e.g. using a timer, and sets the level of the control line 40b to 0 volts (or to a predetermined low level e.g. 1 volt) when a predetermined time has elapsed. The third controller 103 may slowly reduced the level of the control line 40b toO volts, e.g. over a predetermined period of 30 seconds. The third controller 103 may set the level of the control line 40b to a predetermined low level (e.g. 1 volt) for a predetermined period of time, e.g. 5 minutes, before setting it toO volts. The third controller 103 may change the level of the control line 40b to its previous level in response to receiving a high-voltage pulse while the level of the control line 40b is being slowly reduced and/or while it is at the predetermined low level before it is set toO volts. Accordingly, a user can take appropriate action. A user can also use the fourth command provider 304 to switch on the LED lamps in the third zone 23. In a second presence-detection mode (hereinafter referred to as an auto on/auto off mode'), the third controller 103 additionally sets the level of the control line 40b to 10 volts (or to a predetermined high level e.g. 8 volts) in response to a high-voltage pulse on the command line 40c.

Furthermore) the third controller 103 is configured to provide a control signal which also depends upon the level of the control signal received from the fourth zone 24. The level of the control signal received from the fourth zone 24 is hereinafter referred to as the first reference level'. The third controller 103 may operate in one of several dependent modes. For example) in a first dependent mode) the first reference level is used to set the maximum level of the control signal. Accordingly) if the first reference level is e.g. 0 volts, then the LED lamps in the third zone 23 are switched off regardless of any events in the third zone 23. In a second dependent mode, the first reference level is used to set the minimum level of the control signal. Accordingly, if the first reference level is e.g. 10 volts) then the LED lamps in the third zone 23 are switched on at the maximum power regardless of any events in the third zone 23.

In a third dependent mode, the level of the control signal is set to 10 volts (or to a predetermined high level) if the first reference level is above zero. The level of the control signal may also beset independently of the first reference level.

The sequence of levels, the motion-detection modes and/or the dependent modes may be pre-set and/or set and/or selected by a user in any suitable way.

Referring to Figure 9, example operations of the second system 200 will now be described.

At a first time t1, the level of the control line 40b of the third bus 403 isO volts) and the LED lamps in the third zone 23 are off. The level of the control line 40b of the fourth bus 404, i.e. the first reference level, is 10 volts.

At a second time t2, the fifth command provider 30 detects motion and generates a high-voltage pulse on the command line 40c of the third bus 403. The third controller 103 is in a manual-on/auto off mode and so does not change the level of the control line 40b of the third bus 403.

At third) fourth and fifth times t3. t4. t5, the first switch 32 of the fourth command provider 304 is closed, the fourth command provider 304 generates low-voltage pulses on the command line 40c of the third bus 403, and the third controller 103 increases the level of the control line 40b of the third bus 403 from 0 to 2.5 volts, then from 2.5 to 5 volts) and then from 5 to 7.5 volts. The power and brightness of the LED lamps in the third zone 23 increase accordingly.

At a sixth time t5, the second switch 322 of the fourth command provider 304 is closed) the fourth command provider 304 generates a semi-low-voltage pulse on the command line 40c of the third bus 403, the third controller 103 decreases the level of the control line 40b of the third bus 403 from 7.5 to 5 volts, and the power and brightness of the LED lamps in the third zone 23 decrease accordingly.

At seventh and eighth times t7, t8, the motion detector 30 detects motion and generates high-voltage pulses on the command line 40c of the third bus 403.

At a ninth time t9, the time elapsed since the last voltage pulse (i.e. at the eighth time t8) exceeds the predetermined time, and the third controller 103 changes the level of the control line 40b of the third bus 403 toO volts. The LED lamps in the third zone 23 switch off accordingly.

At a tenth time t10. the first switch 32 of the fourth command provider 304 is closed for an extended period of time, the fourth command provider 304 generates a low-voltage pulse on the command line 40c of the third bus 403, the third controller 103 increases the level of the control line 40b of the third bus 403 from 0 to 5 volts, and the power and brightness of the LED lamps in the third zone 23 increase accordingly.

At a similar time, the motion detector 305 detects motion and attempts to generate a high-voltage pulse on the command line 40c of the third bus 403. This is indicated by the dashed line in the figure. However, during the period of overlap between the high and low-voltage pulses, the level of the command line 40c of the third bus 403 remains low. The duration of the high-voltage pulse is shortened or is not present accordingly. The high-voltage pulse may or may not be detected by the third controller 103. In this example, it is not.

At an eleventh time t11, the level of the control line 40b of the fourth bus 404, i.e. the first reference level, decreases from 10 to 0 volts. The third controller 103 is in the first dependent mode and so decreases the level of the control line 40b of the third bus 403 toO volts.

At a twelfth time t12, the first switch 32 of the fourth command provider 304 is closed and the fourth command provider 304 generates a low-voltage pulse on the command line 40c of the third bus 403. The third controller 103 does not increase the level of the control line 40b of the third bus 403 because it is at the maximum level (0 volts) as set by the first reference level.

At a thirteenth time t13, the level of the control line 40b of the fourth bus 404, i.e. the first reference level, changes to 10 volts.

At a fourteenth time t14, the first switch 32 of the fourth command provider 304 is closed, the fourth command provider 304 generates a low-voltage pulse on the command line 40c of the third bus 403, the third controller 103 increases the level of the control line 40b of the third bus 403 from 0 to 2.5 volts, and the power and brightness of the LED lamps in the third zone 23 increase accordingly.

Other variations of the second system 200 Some other variations of the second system 200 will now be described.

In some examples, instead of including a single, fourth command provider 304 and a single, fifth command provider 30, the third zone 23 may include two or more command providers corresponding to switches/dimmers and/or two or more command providers 30 corresponding to presence detectors. The command line 40b of the third bus 403 can carry command signals provided by any number of command providers 304. As will be appreciated, the system 200 generally behaves in a predictable way regardless of any collisions (i.e. overlap) between two or more command signals sent by two or more presence detectors or by two or more presence detectors and a switch/dimmer.

Moreover, in some examples, the fourth command provider 304 (switch/dimmer) may be configured to receive command signals from other command providers corresponding to switches/dimmers, and, in response thereto, to provide an indication to a user (e.g. a visual indication) and/or to inhibit sending of a command signal, e.g. by inhibiting operation of the switches 32, 322. In this way, unpredictable behaviour due to simultaneous operation of switches/dimmers can be indicated to a user and/or avoided.

The third zone 23 need not include any drivers 20 or may include a different number of one or more drivers 20.

The third zone 23 need not include the fourth command provider 304 and/or the fifth command provider 30g.

The third controller 103 need not be connected to the fourth bus 404. In this case, the third controller 103 sees the first reference level as above 10 volts. Accordingly, if the third controller 103 is operating in the first dependent mode, then the control signal can depend upon received command signals and/or internal signals in the normal way.

The third zone 23 need not even include the third controller 103. In this case, the drivers 20 see the level of the command line as above 10 volts and set the power drawn by the LED lamps to the maximum power.

Referring to Figure 10, a fourth controller 104 will now be described. The fourth controller 104 may, for example, be used in the second system 200 in place of the third controller 103.

The fourth controller 104 functions as a controller and/or a command provider (corresponding to a remotely-controllable switch/dimmer). The fourth controller 104 comprises the same features as the second controller 102 (Figure 4). The fourth controller 104 also includes an infrared (IR) receiver lOe for receiving IR signals from a remote controller (not shown). The IR receiver lOe is operatively connected to the microprocessor lOa of the first part 50a and provides internal signals corresponding to received IR signals thereto.

With regard to its function as a controller, the fourth controller 104 operates in the same way as the third controller 103. This is except that the fourth controller 104 can provide a control signal dependent upon the received IR signals. For example, certain received IR signals may be treated as being equivalent to control signals received from other system devices corresponding to switches/dimmers (e.g. the fourth command provider 304). Furthermore, dependences may be set and/or modes may be selected using the remote controller.

With regard to its function as a command provider, the fourth controller 104 can provide command signals via the red connector 46" in response to receiving signals from the remote controller. The command signals provided are preferably the same as those provided by other system devices corresponding to switches/dimmers, i.e. low-voltage or semi-low-voltage pulses. Thus, the fourth controller 104 can function as a command provider (in particular, a switch/dimmer) in e.g. the fourth zone 24.

Referring to Figure 11, a fifth controller 10 will now be described. The fifth controller 105 may, for example) be used in the second system 200 in place of the third controller 103.

The fifth controller 10 functions as a controller and/or a command provider (corresponding to a presence detector). The fifth controller 1O comprises the same features as the second controller 102 (Figure 4). The fifth controller 1O also includes presence-detection circuitry lof operatively connected to the microcontroller lOa. In this example, the presence-detection circuitry 10f includes a passive infrared (PIR) motion detector lOg. However, the presence-detection circuitry lOf may include a different type of presence detector. In response to detecting motion, the presence-detection circuitry lof provides an internal signal to the microcontroller lOa.

With regard to its function as a controller, the fifth controller 105 operates in the same way as the third controller 103. This is except that the microcontroller lOa can receive internal signals from the presence-detection circuitry 101. These internal signals may be treated as being equivalent to command signals received from other system devices corresponding to motion detectors (e.g. the fifth command provider 305). For example, in a manual on/auto off mode, the fifth controller 105 can measures the time elapsed since the last received command signal or the last internal signal. In other examples, the two types of signal may be treated as being different from each other.

With regard to its function as a command provider, the microcontroller ba can receive internal signals from the presence-detection apparatus lof and, in response thereto, provide command signals via the red connector 46" to the fourth bus 404. The command signals provided are preferably the same as those provided by other system devices corresponding to motion detectors (e.g. the fifth command provider 3O), i.e. high-voltage pulses. Thus, the fifth controller 1O can function as a command provider (in particular, a presence detector) in e.g. the fourth zone 24.

In an example application, the third zone 23 may correspond to a room and the fourth zone 24 may correspond to a corridor leading to the room. The fifth controller 105 can control the luminaires 215, 217, 21 in the room and can also provide command signals so that the luminaires (not shown) in the corridor remain on while the room is occupied.

Third system 300 Referring to Figure 12, a third system 300 will now be described. The third system 300 includes fifth and sixth zones 2, 2. The fifth zone 25 includes a fifth bus 40 interconnecting a sixth controller 10, ninth, tenth and eleventh drivers 209, 2011, and a sixth command provider 3O. The sixth controller 105 is connected via a blue connector 46' to the fifth bus 40, and is also connected via a red connector 46" to a first alternative controller 10'. The sixth zone 2 includes a sixth bus 40 interconnecting a seventh controller 107, and twelfth, thirteenth and fourteenth drivers 2012, 2013, 2014. The seventh controller 107 is connected via a blue connector 46' to the sixth bus 40, and is also connected via a red connector 46" to the fifth bus 405. An eighth controller lOg is connected via a red connector 46" to the sixth bus 40g. Each of the drivers 20 2014 is included in a respective luminaire 21 2114. The drivers 20 2014 and the luminaires 21 2114 are the same way as those in the first system 100.

The eighth controller lO comprises the same features as the fifth controller 10 (Figure 11).

In this example, the eighth controller 10 is used only as a command provider (corresponding to a presence detector) and, in this regard, functions as described above in relation to the fifth controller 105. As will be explained in more detail below, the seventh controller 107 is transparent to command signals and so the command signals provided by the eighth controller 10 are received by the sixth controller 10. In an example application, the eighth controller 10 may be located to detect motion in area which is not covered by the sixth controller 10g.

The sixth command provider 30 corresponds to a switch/dimmer and is the same as the fourth command provider 304 (Figure 7). The sixth command provider 30 also provides command signals to the sixth controller 10. In an example application, the sixth command provider 30 may be located near an entrance/exit.

The first alternative controller 10' will now be described in more detail. The first alternative controller 10' includes a blue connector 46' for connecting a cable section 42. The first alternative controller 10' is configured to set the level of the control line 42b in the cable section 42. This is done independently of any command signals on the command line 42c of the cable section 42, which the first alternative controller 10' does not generally receive. In this example, the first alternative controller 10' functions as a potentiometer and enable a user to vary the level of the control line 42b between 0 and 10 volts. The first alternative controller 10' obtains power from the power line 42d of the cable section 42 to do this.

Alternatively or additionally, the first alternative controller 10' may include a switch, e.g. to enable a user to switch the level of the control line 42b from 0 to 10 volts or vice versa. The first alternative controller 10' provides a control signal to the sixth controller 10 and enables a user to vary a reference level (hereinafter referred to as a second reference level) provided thereto.

The sixth controller 10 comprises the same features as the fifth controller 10 (Figure 11). In this example, the sixth controller 105 is used only as a controller and, in this regard, functions as described above in relation to the fifth controller 10. For example, the sixth controller 10 can provide a control signal which is limited to a maximum level set by the second reference level received from the first alternative controller 10', and which depends upon command signals received from the sixth command provider 30 (switch/dimmer) and/or (an absence of) command signals received from the eighth controller 10 (corresponding to a presence detector) and/or internal signals provided by the motion-detection circuitry lOf.

Referring to Figure 13, the seventh controller 107 will now be described in more detail. The seventh controller 107 comprises the same features as the second controller 102 (Figure 4).

This is except that, in place of a single blue connector 46', the seventh controller 107 includes first and second blue connectors 46', 46'2. The ground-line contacts 46a of the first blue connector 46', the second blue connector 46'7 and the red connector 46" are interconnected, as are the command-line contacts 46b and the power-line contacts 46d. Accordingly, the seventh controller 107 is transparent to command signals, i.e. command signals pass through the seventh controller 107 unchanged. The control-line contact 46b of the first blue connectors the second blue connector 46'2 and the red connector 46" are each connected to the interface lob". The seventh controller 107 also includes light-sensor circuitry lOh operatively connected to the microcontroller lOa. The light-sensor circuitry lOh includes a light sensor lOi and provides a signal to the microcontroller lOa that is indicative of the light incident on the light sensor. The level of this signal is hereinafter referred to as the light level.

The light level preferably corresponds to a photopic response. The seventh controller 107 determines an average light level, wherein the averaging is performed over a suitable time period, e.g. 15 minutes. The seventh controller 107 senses the level of the control line 40b of the fifth bus 405, which is connected to the red connector 46". The level of the control line 40b of the fifth bus 40 will be referred to hereinafter as the third reference level.

The first blue connector 46' is used for daylight compensation. The seventh controller 107 is configured to set the control-line contact 46b of the first blue connector 46' to a level which depends upon the third reference level, the light level and/or a target level. For example, the seventh controller 107 may adjust the level so that the light level is equal to a target level (for background light levels below a certain level) and also so that the level is either less than or more than the third reference level. The target light level may be pre-set and/or set by a user

in any suitable way.

The second blue connector 46'7 is used for twilight switching. The seventh controller 107 is configured to set the level of the control-line contact 46b of the second blue connector 46'7 to a predetermined twilight level, e.g. 1 volt, when the average light level is below a threshold level, or, otherwise, to the third reference level. The threshold level may be pre-set and/or set by a user in any suitable way.

In this example, the sixth bus 405 is connected to the first blue connector 46' of the seventh controller 107. However, the sixth bus 40 could instead be connected to the second blue connector 46'7. Buses 40 and system devices could be connected to both the first and second blue connectors 46', 46'7. In some examples, the seventh controller 107 may only include features required to function as a daylight compensator or a twilight switch.

Other variations of the third system 300 Some other variations of the third system 300 will now be described.

The third system 300 need not include the sixth command provider 30 (switch/dimmer) and/or the eighth controller log (presence detector).

The third system 300 need not include the sixth command provider 30 the sixth controller and the eighth controller log. In this case, the overall light levels are controlled by the first alternative controller 10'.

The third system 300 need not include the sixth command provider 305 (switch/dimmer). The third system 300 need not include the seventh controller 107. Instead of the first alternative controller 10' and the sixth controller 105, the third system may include a controller 10 which is the same as the fourth controller 104 (remotely-controllable switch/dimmer).

Fourth system 400 Referring to Figure 14, a part of a fourth system 400 will now be described. The fourth system 400 includes seventh, eighth and ninth zones 27, 2, 2. The seventh zone 27 includes a seventh bus 407 interconnecting a ninth controller 10 and a seventh command provider 307.

The ninth controller 10 is connected via a blue connector 46' to the seventh bus 40, and is also connected via a red connector 46" to a second alternative controller 10'2. The eighth zone 2 includes an eighth bus 40 interconnecting a tenth controller 1010 and one or more other system devices (not shown). The ninth zone 29 includes a ninth bus 409 interconnecting an eleventh controller 1011 and one or more other system devices (not shown). The tenth and eleventh controllers lO11are connected via respective blue connectors 46' to the eighth and ninth zones 2, 29 respectively, and also connected via respective red connectors 46" to the seventh bus 407.

Each of the ninth, tenth and eleventh controllers 10, 1010, 1011 comprises the same features as the fourth controller 104 (Figure 10).

The second alternative controller 10'7 is the same as the first alternative controller 10' (Figure 12) except that the potentiometer is pre-set. The second alternative controller 10'7 provides a constant reference level of e.g. 2.5 volts (hereinafter referred to as the fourth reference level) to the ninth controller 10g.

The seventh command provider 307 corresponds to a switch/dimmer and comprises the same features as the fourth command provider 304 (Figure 7), except that it does not include the second switch 322 and the diodes and provides only low-voltage pulses.

The eighth controller 10 is configured to provide a control signal which is switched between the fourth reference level, e.g. 2.5 volts, and 10 volts in response to a command signal (low-voltage pulse) received from the seventh command provider 307. The control signal provided by the eighth controller 10 is used as a reference level (hereinafter referred to as the fifth reference level) by the tenth and eleventh controllers 1010, 1011.

The tenth and eleventh controllers 1010, 1011 are configured to operate in the first dependent mode, in which the fifth reference level is used to set the maximum level of the control signal.

In an example application) the seventh command provider 307 can be used to switch between a normal mode and a low-power mode. When the fourth system 400 is in the low-power mode, LED lamps (not shown) in the eighth and ninth zones 28, 29 are limited to a low power and brightness suitable for e.g. after-hours maintenance.

Instead of there being two zones 2 connected to the seventh zone 27, there may be only one zone 2, or there may be three or more zones 2. Furthermore, there may be one or more zones connected to one or more of the zones 2 connected to the seventh zone 27.

Fifth system 500 Referring to Figure 15, a fifth system 500 will now be described. The fifth system 500 includes tenth, eleventh and twelfth zones 210, 212. The tenth zone includes a bus 40 interconnecting a controller 1012 and a driver The eleventh zone 211 includes a bus 4Oii interconnecting a controller 1013 and a driver The twelfth zone 212 includes a bus °12 interconnecting a main controller 1014, a command provider 30, and a driver The drivers 2015, 2017 are included in respective luminaire 2115, 2117. The main controller 1014 in the twelfth zone 212 is connected via a blue connector 46' to the bus 4012 in the twelfth zone 212, and via a red connector 46" to the bus in the tenth zone An additional controller 1015 is connected via a blue connector 46' to the bus °12 in the twelfth zone 212, and via a red connector 46" to the bus 40 in the eleventh zone 2.

The main controller 1014 is configured to control operation of the twelfth zone 212, e.g. in any of the hereindescribed ways. For example, the main controller 1014 may send a control signal to the driver 2017 in the twelfth zone 212 dependent upon command signals received from the command provider 30 in the twelfth zone 212 and/or upon the control signal received from the bus 40 of the tenth zone 2o and/or upon internal signals. Furthermore, the main controller 1014 is configured to send command signals via the bus in the tenth zone 2o to the controller 1012 in the tenth zone 2o The command signals sent may correspond to those received from the command provider 30 in the twelfth zone 212. However, this need not be the case. For example, if the twelfth zone 212 includes different types of command providers providing different types of command signals (e.g. switches/dimmers and motion detectors)) then the main controller 1014 may only send selected types of command signals. In other words, the main controller 1014 may act as a command signal filter.

The additional controller 1015 is configured not to change the level of the command line of the bus °12 in the twelfth zone 212, i.e. not to send a control signal. Accordingly, the twelfth zone 212 is controlled only by the main controller 1014. The additional controller 105 is configured to send command signals via the bus 40 in the eleventh zone to the controller 1013 in the eleventh zone The command signals sent may be determined in any of the ways described above in relation to the main controller 1014.

Accordingly, in the fifth system 500, command signals from one zone (the twelfth zone 212) can be sent to two other zones (the tenth and eleventh zones 2io, 211).

In other examples, the tenth, eleventh and twelfth zones 210, 211, 212 may include different system devices. In some examples, the twelfth zone 212 may not include any drivers 20 and the main controller 1014 may be configured not to send the control signal. Accordingly, the twelfth zone 212 is merely for providing command signals to the tenth and eleventh zones In other examples, the fifth system 500 may include any number of three or more zones 2, any two or more of which may correspond to the tenth and eleventh zones and any one or more of which may correspond to the twelfth zone 212 Sixth system 600 Referring to Figure 16, a sixth system 600 is shown. The sixth system 600 includes sixteen interconnected zones 2. However, there may be any number of two or more zones 2. Each zone 2 is connected to one or more other zones 2. Each connection is via a controller (not shown) comprising the same features as the second controller 102 (Figure 4). Each controller is configured such that the control signal in the zone 2 can be dependent upon the control signal in the other zones 2 (represented by downwards-pointing arrows in the figure) and/or that command signals and/or internal signals in the zone 2 can be provided to the other zone (represented by upwards-pointing arrows in the figure). The zones 2 can be connected in any way, provided that the control signal in a zone 2 is dependent upon only one other zone 2.

The zones 2 form a hierarchy of zones 2, wherein zones 2 may have one or more dependent zones 2 (i.e. zones 2 in which the control signal is dependent upon the control signal in the zone 2). Each zone 2 with one or more dependent zones 2 may be dependent upon another zone 2, or it may be independent. Zones 2 can also provide command signals to one or more other zones 2 (and, in some cases, thence to one or more other zones 2).

Accordingly, in some examples, operation of several dependent zones 2 can be controlled from a single zone 2. For example, a particular zone 2 can be connected to several dependent zones 2, either directly or via one or more other zones 2. The particular zone 2 may be configured to provide a control signal which defines, for example, the maximum, minimum or actual level of the control signal in each of the dependent zones. Furthermore, in some examples, command signals can be provided from a particular zone 2 to several other zones 2.

This provides a different way in which the behaviour of several zones 2 can be controlled from a single zone 2. It will be appreciated that countless different systems can be provided to meet different needs.

Override bus In some examples, a system may include an override bus in addition to one or more buses 40.

The override bus can be connected to one or more of the controllers 10 and/or command providers 30 in the system, and/or to one or more of the buses in the system, and/or to the power supply that supplies the power via a power line to the luminaires 21 in the system. An example of such a power supply is described in Wa 2010/106375 A2. Like a bus 40, the override bus includes one or more cable sections 42 and may include one or more tee connectors 44. controller io, command providers 30 and the power supply may include a third type of connector 46 (hereinafter referred to as a white connector') for connecting to the override bus. The override bus can be connected to buses 40 using a tee connector 44.

The override bus includes a ground line, a control line and a power line that are equivalent to the corresponding lines of a bus 40. At a controller 10 and/or a command provider 30, the ground line and the power line of the override bus may be connected to the corresponding lines of one or more buses 40. The level of the control line of the override bus can be set to a predetermined level, e.g. grounded, by a controller 10, a command provider 30 or the power supply in response to an action, e.g. operation of a switch. In response to detecting that the level of the control line is low, e.g. less than a threshold level of 0.5 volts, the power supply is configured to provide a soft-off signal via the power line to the drivers 30. In this example, the power supply provides the soft-off signal by modulating the frequency of the high-frequency AC power in the power line, e.g. by changing the frequency from 50 toSS kilohertz with a 1% duty cycle. However, the soft-off signal can be provided in any suitable way. Furthermore) the level of the control line 40b in buses 40 connected to the override bus is automatically set low when the level of the control line in the override bus is grounded. Thus, the override bus provides other ways of switching off LED lamps in the system. Moreover, this can be done without necessarily switching off the power supply. The override bus may also include a command line that is equivalent to the command line of the bus 40 and can be used for communications between system devices and/or the power supply.

Further devices Referring to Figure 17, a sixteenth controller 105 will now be described. The sixteenth controller 1015 includes features of the fourth controller 104 (remotely controllable switch/dimmer), the fifth controller 10 (corresponding to a presence detector) and the seventh controller 107 (light sensor). The sensors associated with the infrared receiver and the PIR motion detector are included within a housing 10]. The sensor associated with the light sensor is included behind a lens 10k. A reflector 101 is also provided. The reflector 101 includes, for example, a sheet of plastics material coated with a reflective material. The reflector 101 may be adapted to be removably connectable to the sixteenth controller 1015.

When connected to the sixteenth controller 1015, the reflector 101 may be rotatable around two axes. Such a reflector 101 enables a user to change the field of view and/or the sensitivity of the sensors included in the sixteenth controller Referring to Figure 18, a power-line-communication (PLC) device 50 will now be described.

The PLC device 50 is for use with a power distribution system including a power distribution line which includes a twisted pair of elongate conductors. An example of such a system is described WO 2010/106375 A2. The PLC device 50 includes a splittable ferrite element 50a for connecting around a section of one of the conductors (not shown). The PLC device 50 also includes a connector Sob for connecting to a cable section 42. The PLC device 50 is configured to receive control and/or command signals from the cable section 42 and, in response thereto, to send corresponding power-distribution-line signals via a particular virtual channel of the power distribution line. The PLC device 50 is also configured to receive power-distribution-line signals which have been sent via the same virtual channel of the power distribution line and, in response thereto, to send corresponding control and/or command signals from the cable section 42, or to change the level of such signals. In this example, the PLC device 50 includes a selector SOc to enable a user to select one of several (e.g. 16) virtual channels. However) an individual PLC device 50 may communicate via only one virtual channel. Accordingly) two or more PLC devices 50 can be used to interconnect two or more separate parts of a bus 2. Thus, the amount of cabling can be reduced, e.g. in widely-distributed systems.

A central PLC device (not shown) will now be described. In contrast to PLC devices 50, which merely forward control and/or command signals between two or more parts of a bus 40, the central PLC device 50 can send and receive signals via another communications network) e.g. a DALI or DMX network, and can send and receive corresponding control and/or command signals to any PLC device 50 associated with any bus 40.

Referring to Figure 19) a power harvester 60 will now be described. The power harvester 60 is for use with a power distribution system as described above. The power harvester 80 includes a splittable ferrite element 60a for connecting around a length of one of the conductors of the power distribution line (not shown). The power harvester 60 also includes a connector 60b for connecting to a cable section 42. The power harvester 60 is configured to draw an amount of power, e.g. 1000 or 2000 milliwatts, from the power distribution line and to provide a suitable voltage and current to the power line 40d of a bus 40. Thus, the amount of the power available on the bus 40 can be increased) e.g. where system devices connected thereto have particularly high power demands. Kit

A kit including at least one controller 10, at least one driver 20) at least one command provider 10, at least one cable section 42 and at least one tee connector 44 may be provided.

A user can use the kit to install a system to meet a particular need. A user can also maintain the system, e.g. if a particular part of the system fails, and can change the system as required, e.g. by adding system devices to zones 2 and/or by adding zones 2 to the system. The modular nature of the system, and the way in which system devices and other devices are interconnected by buses 40 means that these operations can be carried out relatively easily.

Other modifications It will be appreciated that many other modifications may be made to the embodiments hereinbefore described.

For example) the systems may alternatively or additionally be used to control operation of other types of electrical devices, e.g. heating or cooling devices.

Drivers 20 need not be included in luminaires 21. Drivers 20 may be provided separately from luminaires 21 and may be operatively connectable thereto.

Devices need not provide power to, or draw power from, the power line 40d of a bus 40. For example, such devices may include a source of power e.g. a battery.

Controllers 10 and command providers 20 may include different user interfaces (e.g. scene setters), different sensors (e.g. pressure sensors) and/or different communications interfaces (e.g. Ethernet, Wi-Fi or Bluetooth communication interfaces).

It will be appreciated that countless different systems can be provided using the abovedescribed controllers 10, drivers 20, command providers 30, buses 40, override buses, PLC devices 50, central PLC devices, and power-harvesters 60. For example, any of the abovedescribed zones 2 may include any appropriate ones of the abovedescribed devices.

Furthermore) a system may include any two or more of the abovedescribed zones 2 and these may be interconnected in any suitable way.

Claims

Claims 1. A system suitable for controlling operation of a plurality of electrical devices) particularly luminaires, the system comprising: -at least one zone comprising: -a bus; -at least one command provider connected to the bus and configured to provide a command signal thereto in response to an action; -a controller connected to the bus and configured to receive command signals therefrom and to provide an analogue control signal thereto dependent upon the command signals; and -at least one driver connected to the bus and configured to receive the control signal therefrom, and associated with at least one of the plurality of electrical devices and configured to control operation thereof in dependence upon the control signal.

2. A system according to claim 1, wherein the at least one command provider, the controller and the at least one driver are devices which are remote from one another.

3. A system according to claim 1 or 2, comprising a plurality of zones, wherein each of the plurality of zones comprises a plurality of drivers associated with a plurality of electrical devices, and wherein electric devices associated with the same zone are caused to operate in the same way.

4. A system according to any preceding claim, wherein at least one driver is configured to control the power used by the associated at least one electrical device, and wherein the power is a function of the level of the control signal.

5. A system according to any preceding claim, comprising first and second zones, wherein the controller of the second zone is connected to the bus of the first zone and configured to receive the control signal therefrom, and wherein the control signal provided to the bus of the second zone is dependent upon the control signal received from the bus of first zone.

6. A system according to claims, wherein the control signal provided to the bus of the second zone is determined in such a way that it is either no larger than or no smaller than the control signal received from the bus of the first zone.

7. A system according to claims or 6, comprising a tree network of zones comprising a zone of a first type and a plurality of zones of a second type, wherein the controller in each zone of the second type is connected to the bus of another zone in the tree network and is configured to receive the control signal therefrom, and wherein the control signal provided to the bus of each zone of the second type is dependent upon the control signal on the bus of the zone of the first type.

8. A system according to any preceding claim, comprising first and second zones, wherein the controller of the second zone is connected to the bus of the first zone and configured to provide command signals thereto.

9. A system according to any preceding claim, wherein the bus comprises a conductor for carrying the command signal and another conductor for carrying the control signal.

10. A system according to any preceding claim, wherein at least one zone comprises a plurality of command providers connected to a conductor comprised in the bus.

11. A system according to any preceding claim, wherein at least one zone comprises a plurality of drivers connected to a conductor comprised in the bus.

12. A system according to any preceding claim, wherein only one controller is connected to the bus.

13. A system according to any preceding claim, wherein communications between the at least one command provider and the controller, and between the controller and the at least one driver are simplex.

14. A system according to any preceding claim, comprising first and second zones, wherein signals on the bus of the first zone are not provided to the bus of the second zone and vice versa.

15. A system according to any preceding claim: -wherein the bus comprises a first conductor for carrying the command signals, wherein the first conductor is loosely held at a first voltage; and -wherein at least one command provider is configured to set the first conductor to a voltage different from the first voltage in response to the action, thereby providing a command signal.

16. A system according to claim 15, wherein the controller is configured to loosely hold the first conductor at the first voltage.

17. A system according to claim 15 or 16, wherein the command signal corresponds to a voltage pulse.

18. A system according to any one of claims 15 to 17, wherein at least one command provider comprises a switch configured to connect the first conductor to a voltage reference to provide a command signal.

19. A system according to claim 18: -wherein at least one of a first type of command provider comprises a switch configured to connect the first conductor to a first voltage reference via a path with a first impedance to provide a first type of command signal; -wherein at least one of a second type of command provider comprises a switch configured to connect the first conductor to a second voltage reference via a path with a second impedance to provide a second type of command signal; and -wherein the first impedance is less than the second impedance, such that the first type of command signal has priority over the second type of command signal.

20. A system according to any one of claims 15 to 19: -wherein the bus further comprises a second conductor, wherein the second conductor is grounded; and -wherein at least one of a first type of command provider comprises a switch configured to connect the first and second conductors to provide a command signal.

21. A system according to claim 20: -wherein at least one of the first type of command provider comprises a further switch configured to provide a further command signal at a voltage between the first voltage and ground.

22. A system according to any preceding claim: -comprising at least one of a first type of command provider configured to provide a first type of command signal and at least one of a second type of command provider configured to provide a second type of command signal different from the first type of command signal; and -wherein the controller is configured to provide a control signal differently dependent upon the first and second types of command signals.

23. A system according to any preceding claim: -comprising at least one of a first type of command provider comprising a user interface and configured to provide a command signal of a first type in response to a user input; and -wherein the controller is configured to change the control signal from a first level to a second level different from the first level in response to receiving a command signal of the first type.

24. A system according to clam 23, wherein the first and second levels are comprised in a sequence of levels.

25. A system according to clam 23 or 24, wherein the at least one driver is configured to switch on the associated at least one electrical device when the control signal changes from the first level to the second level, and is configured to switch off the associated at least one electrical device when the control signal changes from the second level to the first level.

26. A system according to any preceding claim: -comprising at least one of a second type of command provider comprising a sensor and configured to provide a command signal of a second type in response to a detection event; -wherein the controller is configured to change the control signal from a first level to a second level different from the first level in response to receiving a command signal of the second type; and -wherein the at least one driver is configured to switch on the associated at least one electrical device when the control signal changes from the first level to the second level.

27. A system according to any preceding claim: -comprising at least one of a second type of command provider comprising a sensor and configured to provide a command signal of a second type in response to a detection event; -wherein the controller is configured to change the control signal from a second level to a first level different from the first level in response to determining that the time elapsed since a command signal of the second type or of another type was last received is equal to or greater than a predetermined time; and -wherein the at least one driver is configured to switch off the associated at least one electrical device when the control signal changes from the second level to the first level.

28. A system according to claim 26 or 27, wherein the second type of command provider comprises a presence detector.

29. A system according to any preceding claim: -wherein at least one driver is configured to provide power to the bus, wherein the power is obtained from power provided by a power line, wherein the power line is for distributing power to the plurality of electrical devices; and -wherein the controller and/or at least one command provider is configured to obtain power from the bus.

30. A system according to any preceding claim, comprising first and second zones, wherein the controller of the second zone is connected to the bus of the first zone and corresponds to a command provider comprised in the first zone.

31. A system according to any preceding claim, wherein the controller of at least one zone is configured to receive internal signals from apparatus associated with the controller and to provide an analogue control signal to the bus dependent upon the internal signals.

32. A system according to any preceding claim, wherein the controller of at least one zone is configured to receive internal signals from apparatus associated with the controller, is connected to the bus of another zone, and is configured to provide command signals thereto dependent upon the internal signals.

33. A system according to claim 31 or 32, wherein the apparatus comprises a user interface, a detector, and/or a communications interface for communicating with a remote device.

34. A system according to any preceding claim, wherein the controller has a plurality of operating modes corresponding to a plurality of ways in which the analogue control signal is provided dependent upon received signals.

35. A system according to any preceding claim, comprising at least one other zone comprising another controller in place of the controller, the other controller configured to provide the control signal to the bus in the other zone independently of any command signals.

36. A system according to claim 35, wherein the other controller is configured to provide the control signal using power obtained from the bus.

37. A system according to any preceding claim: -comprising first and second zones; -wherein the second zone comprises a controller comprising a light sensor configured to sense a light level; -wherein the controller comprising the light sensor is connected to the bus of the first zone and configured to obtain the control signal therefrom, and is connected to the bus of the second zone and configured to provide a control signal thereto which is dependent upon the control signal received from the bus of the first zone and/or upon the light level.

38. A system according to claim 37, wherein the control signal provided to the bus of the second zone is reduced dependent upon the light level.

39. A system according to claim 37 or 38, wherein the control signal provided to the bus of the second zone corresponds to a predetermined level when the light level is less than or equal to a predetermined level, and otherwise corresponds to the control signal received from the bus of the first zone.

40. A system according to any preceding claim: -comprising a power supply for supplying power via a power line to the plurality of electrical devices; -comprising an additional bus; -wherein at least one command provider and/or the controller of at least one zone is connected to the additional bus and is configured to provide an off signal thereto in response to an action; -wherein the power supply is connected to the additional bus and is configured to receive the off signal therefrom and, in response thereto, to provide a further off signal via the power line to the at least one driver; and -wherein the at least one driver is configured to received the further off signal and) in response thereto) to switch off the associated at least one electrical device.

41. A system according to any preceding claim: -comprising an additional bus connected to the bus of at least one zone; -wherein at least one command provider and/or the controller of at least one zone and/or a power supply for supplying power to the plurality of electrical devices is connected to the additional bus and is configured to provide an off signal thereto in response to an action, wherein providing the off signal comprises grounding a conductor included in the additional bus; -wherein the bus includes a conductor for carrying the control signal; and -wherein the additional bus is connected to the bus such that, when the conductor in the additional bus is grounded, so too is the conductor for carrying the control signal, thereby causing the at least one driver to switch off the associated at least one electrical device.

42. A system according to claim 40 or 41: -wherein at least one command provider, the controller of at least one zone and/or the power supply is configured to provide an additional command signal to the additional bus in response to an action; and -wherein the controller of the at least one zone and/or the power supply is configured to receive the additional command signal from the additional bus and, in response thereto, to cause at least one of the plurality of electrical devices to switch off.

43. A system according to any preceding claim, wherein the bus of at least one zone is divided into two or more separate parts, wherein each part is connected to a power line communication device, wherein each power line communication devices is also connectable to a power line, wherein the power line is for distributing power to the plurality of electrical devices.

44. A system according to claim 43, comprising first and second zones, wherein the bus of each of the first and second zones is divided into two or more parts, wherein each part of the bus of the first zone is connected to a power line communication device configured to communicate via a first channel of the power line, and wherein each part of the bus of the second zone is connected to a power line communication device configured to communicate via a second channel of the power line.

45. A system according to claim any preceding claim, comprising: -at least one power line communication device of a first type connected to a bus and connectable to a power line, wherein the power line is for distributing power to the plurality of electrical devices; and -a power line communication device of a second type connectable to the power line and configured to send and/or receive command signals and/or control signals to and/or from the bus via the at least one power line communication device of the first type.

45. A system according to any preceding claim, comprising at least one device connected to a bus and connectable to a power line, wherein the power line is for distributing power to the plurality of electrical devices, wherein the device is configured to obtain power from the power line and provide the power to the bus for powering devices connected thereto.

47. A system according to any preceding claim: -wherein at least one command provider is configured to provide a command signal of another type to the bus in response to another action; and -wherein the controller of at least one zone is configured: -to provide the control signal independently of the command signal of the other type; and, -in response to receiving the command signal of the other type, to provide an indication thereof and/or to provide a command signal of the other type to a bus of another zone to which the controller is connected.

48. A system according to claim 47, wherein the other action includes determining that an error has occurred.

49. A system according to any preceding claim, comprising at least one other zone without any command providers, without any controllers and/or without any drivers.

50. A system according to any preceding claim, comprising at least one command provider configured to receive a command signal from the bus and, in response thereto, to provide an indication thereof and/or to temporarily refrain from sending a command signal in response to an action.

51. A kit of parts for assembly into a system according to any preceding claim, the kit comprising at least one command provider, the controller and at least one driver.

52. A kit according to claim 51, comprising a plurality of cable sections and at least one tee connector for assembly into the bus, wherein each of the plurality of cable sections is connectable to the tee connector, the command provider, the controller and the driver.

53. A controller suitable for use as part of a system according to any preceding claim: -the controller comprising: -a first connector for connecting to a first bus; and -a second connector for connecting to a second bus; -the controller configured to: -receive command signals from the first bus via the first connector, wherein the command signals are provided to the first bus by at least one command provider in response to action; -receive a second analogue control signal from the second bus via the second connector, wherein the second control signal is provided to the second bus by another controller; and -provide a first analogue control signal to the first bus via the first connector dependent upon the command signals and/or the second control signal.

54. A command provider, controller or driver as specified in any preceding claim.Amendments to the claims have been filed as follows Claims 1. A system suitable for controlling operation of a plurality of electrical devices, particularly luminaires, the system comprising: -at least one zone comprising: -a bus; -at least one command provider connected to the bus and configured to provide a command signal thereto in response to an action; -a controller connected to the bus and configured to receive command signals therefrom and to provide an analogue control signal thereto dependent upon the command signals; and -at least one driver connected to the bus and configured to receive the control signal therefrom, and associated with at least one of the plurality of electrical devices and configured to control operation thereof in dependence upon the control signal.2. A system according to claim 1, wherein the at least one command provider, the controller and the at least one driver are devices which are remote from one another.3. A system according to claim 1 or 2, comprising a plurality of zones, wherein each of the plurality of zones comprises a plurality of drivers associated with a plurality of electrical devices, and wherein electric devices associated with the same zone are caused to operate in the same way.4. A system according to any preceding claim, wherein at least one driver is configured to control the power used by the associated at least one electrical device, and wherein the power is a function of the level of the control signal.5. A system according to any preceding claim, comprising first and second zones, wherein the controller of the second zone is connected to the bus of the first zone and configured to receive the control signal therefrom, and wherein the control signal provided to the bus of the second zone is dependent upon the control signal received from the bus of first zone.6. A system according to claim 5, wherein the control signal provided to the bus of the second zone is determined in such a way that it is either no larger than or no smaller than the control signal received from the bus of the first zone.7. A system according to claim 5 or 6, comprising a tree network of zones comprising a zone of a first type and a plurality of zones of a second type, wherein the controller in each zone of the second type is connected to the bus of another zone in the tree network and is configured to receive the control signal therefrom, and wherein the control signal provided to the bus of each zone of the second type is dependent upon the control signal on the bus of the zone of the first type.8. A system according to any preceding claim, comprising first and second zones, wherein the controller of the second zone is connected to the bus of the first zone and configured to provide command signals thereto.9. A system according to any preceding claim, wherein the bus comprises a conductor for carrying the command signal and another conductor for carrying the control signal.10. A system according to any preceding claim, wherein at least one zone comprises a r plurality of command providers connected to a conductor comprised in the bus.11. A system according to any preceding claim, wherein at least one zone comprises a plurality of drivers connected to a conductor comprised in the bus.12. A system according to any preceding claim, wherein only one controller is connected to the bus.13. A system according to any preceding claim, wherein communications between the at least one command provider and the controller, and between the controller and the at least one driver are simplex.14. A system according to any preceding claim, comprising first and second zones, wherein signals on the bus of the first zone are not provided to the bus of the second zone and vice versa.15. A system according to any preceding claim: -wherein the bus comprises a first conductor for carrying the command signals, wherein the first conductor is loosely held at a first voltage; and -wherein at least one command provider is configured to set the first conductor to a voltage different from the first voltage in response to the action, thereby providing a command signal.16. A system according to claim 15, wherein the controller is configured to loosely hold the first conductor at the first voltage.17. A system according to claim 15 or 16, wherein the command signal corresponds to a voltage pulse.18. A system according to any one of claims 15 to 17, wherein at least one command provider comprises a switch configured to connect the first conductor to a voltage reference to r provide a command signal.19. A system according to claim 18: -wherein at least one of a first type of command provider comprises a switch configured to connect the first conductor to a first voltage reference via a path with a first impedance to provide a first type of command signal; -wherein at least one of a second type of command provider comprises a switch configured to connect the first conductor to a second voltage reference via a path with a second impedance to provide a second type of command signal; and -wherein the first impedance is less than the second impedance, such that the first type of command signal has priority over the second type of command signal.20. A system according to any one of claims 15 to 19: -wherein the bus further comprises a second conductor, wherein the second conductor is grounded; and -wherein at least one of a first type of command provider comprises a switch configured to connect the first and second conductors to provide a command signal.21. A system according to claim 20: -wherein at least one of the first type of command provider comprises a further switch configured to provide a further command signal at a voltage between the first voltage and ground.22. A system according to any preceding claim: -comprising at least one of a first type of command provider configured to provide a first type of command signal and at least one of a second type of command provider configured to provide a second type of command signal different from the first type of command signal; and -wherein the controller is configured to provide a control signal differently dependent upon the first and second types of command signals.23. A system according to any preceding claim: -comprising at least one of a first type of command provider comprising a user interface r.and configured to provide a command signal of a first type in response to a user input; and -wherein the controller is configured to change the control signal from a first level to a second level different from the first level in response to receiving a command signal of the first type.24. A system according to clam 23, wherein the first and second levels are comprised in a sequence of levels.25. A system according to clam 23 or 24, wherein the at least one driver is configured to switch on the associated at least one electrical device when the control signal changes from the first level to the second level, and is configured to switch off the associated at least one electrical device when the control signal changes from the second level to the first level.26. A system according to any preceding claim: -comprising at least one of a second type of command provider comprising a sensor and configured to provide a command signal of a second type in response to a detection event; -wherein the controller is configured to change the control signal from a first level to a second level different from the first level in response to receiving a command signal of the second type; and -wherein the at least one driver is configured to switch on the associated at least one electrical device when the control signal changes from the first level to the second level.27. A system according to any preceding claim: -comprising at least one of a second type of command provider comprising a sensor and configured to provide a command signal of a second type in response to a detection event; -wherein the controller is configured to change the control signal from a second level to a first level different from the second level in response to determining that the time elapsed C since a command signal of the second type or of another type was last received is equal to or greater than a predetermined time; and -wherein the at least one driver is configured to switch off the associated at least one electrical device when the control signal changes from the second level to the first level.28. A system according to claim 26 or 27, wherein the second type of command provider comprises a presence detector.29. A system according to any preceding claim: -wherein at least one driver is configured to provide power to the bus, wherein the power is obtained from power provided by a power line, wherein the power line is for distributing power to the plurality of electrical devices; and -wherein the controller and/or at least one command provider is configured to obtain power from the bus.30. A system according to any preceding claim, comprising first and second zones, wherein the controller of the second zone is connected to the bus of the first zone and corresponds to a command provider comprised in the first zone.31. A system according to any preceding claim, wherein the controller of at least one zone is configured to receive internal signals from apparatus associated with the controller and to provide an analogue control signal to the bus dependent upon the internal signals.32. A system according to any preceding claim, wherein the controller of at least one zone is configured to receive internal signals from apparatus associated with the controller, is connected to the bus of another zone, and is configured to provide command signals thereto dependent upon the internal signals.33. A system according to claim 31 or 32, wherein the apparatus comprises a user interface, a detector, and/or a communications interface for communicating with a remote device.0 34. A system according to any preceding claim, wherein the controller has a plurality of operating modes corresponding to a plurality of ways in which the analogue control signal is provided dependent upon received signals.35. A system according to any preceding claim, comprising at least one other zone comprising another controller in place of the controller, the other controller configured to provide the control signal to the bus in the other zone independently of any command signals.36. A system according to claim 35, wherein the other controller is configured to provide the control signal using power obtained from the bus.37. A system according to any preceding claim: -comprising first and second zones; -wherein the second zone comprises a controller comprising a light sensor configured to sense a light level; -wherein the controller comprising the light sensor is connected to the bus of the first zone and configured to obtain the control signal therefrom, and is connected to the bus of the second zone and configured to provide a control signal thereto which is dependent upon the control signal received from the bus of the first zone and/or upon the light level.38. A system according to claim 37, wherein the control signal provided to the bus of the second zone is reduced dependent upon the light level.39. A system according to claim 37 0138, wherein the control signal provided to the bus of the second zone corresponds to a predetermined level when the light level is less than or equal to a predetermined level, and otherwise corresponds to the control signal received from the bus of the first zone.40. A system according to any preceding claim: -comprising a power supply for supplying power via a power line to the plurality of electrical devices; -comprising an additional bus; C -wherein at least one command provider and/or the controller of at least one zone is connected to the additional bus and is configured to provide an off signal thereto in response to an action; -wherein the power supply is connected to the additional bus and is configured to receive the off signal therefrom and, in response thereto, to provide a further off signal via the power line to the at least one driver; and -wherein the at least one driver is configured to received the further off signal and, in response thereto) to switch off the associated at least one electrical device.41. A system according to any preceding claim: -comprising an additional bus connected to the bus of at least one zone; -wherein at least one command provider and/or the controller of at least one zone and/or a power supply for supplying power to the plurality of electrical devices is connected to the additional bus and is configured to provide an off signal thereto in response to an action, wherein providing the off signal comprises grounding a conductor included in the additional bus; -wherein the bus includes a conductor for carrying the control signal; and -wherein the additional bus is connected to the bus such that, when the conductor in the additional bus is grounded, so too is the conductor for carrying the control signal, thereby causing the at least one driver to switch off the associated at least one electrical device.42. A system according to claim 40 or 41: -wherein at least one command provider, the controller of at least one zone and/or the power supply is configured to provide an additional command signal to the additional bus in response to an action; and -wherein the controller of the at least one zone and/or the power supply is configured to receive the additional command signal from the additional bus and, in response thereto, to cause at least one of the plurality of electrical devices to switch off.43. A system according to any preceding claim, wherein the bus of at least one zone is divided into two or more separate parts, wherein each part is connected to a power line communication device, wherein each power line communication devices is also connectable to a power line, wherein the power line is for distributing power to the plurality of electrical devices. Co44. A system according to claim 43, comprising first and second zones, wherein the bus of each of the first and second zones is divided into two or more parts, wherein each part of the bus of the first zone is connected to a power line communication device configured to communicate via a first channel of the power line, and wherein each part of the bus of the second zone is connected to a power line communication device configured to communicate via a second channel of the power line.45. A system according to claim any preceding claim, comprising: -at least one power line communication device of a first type connected to a bus and connectable to a power line, wherein the power line is for distributing power to the plurality of electrical devices; and -a power line communication device of a second type connectable to the power line and configured to send and/or receive command signals and/or control signals to and/or from the bus via the at least one power line communication device of the first type.46. A system according to any preceding claim, comprising at least one device connected to a bus and connectable to a power line, wherein the power line is for distributing power to the plurality of electrical devices, wherein the device is configured to obtain power from the power line and provide the power to the bus for powering devices connected thereto.47. A system according to any preceding claim: -wherein at least one command provider is configured to provide a command signal of another type to the bus in response to another action; and -wherein the controller of at least one zone is configured: -to provide the control signal independently of the command signal of the other type; and, -in response to receiving the command signal of the other type, to provide an indication thereof and/or to provide a command signal of the other type to a bus of another zone to which the controller is connected.48. A system according to claim 47, wherein the other action includes determining that an error has occurred. r49. A system according to any preceding claim, comprising at least one other zone without any command providers, without any controllers and/or without any drivers.50. A system according to any preceding claim, comprising at least one command provider configured to receive a command signal from the bus and, in response thereto, to provide an indication thereof and/or to temporarily refrain from sending a command signal in response to an action.51. A kit of parts for assembly into a system according to any preceding claim, the kit comprising at least one command provider, the controller and at least one driver.52. A kit according to claim 51, comprising a plurality of cable sections and at least one tee connector for assembly into the bus, wherein each of the plurality of cable sections is connectable to the tee connector, the command provider, the controller and the driver.53. A controller suitable for use as part of a system according to any preceding claim: -the controller comprising: -a first connector for connecting to a first bus; and -a second connector for connecting to a second bus; -the controller configured to: -receive command signals from the first bus via the first connector, wherein the command signals are provided to the first bus by at least one command provider in response to action; -receive a second analogue control signal from the second bus via the second connector, wherein the second control signal is provided to the second bus by another controller; and -provide a first analogue control signal to the first bus via the first connector dependent upon the command signals and/or the second control signal.54. A command provider or controller as specified in any preceding claim.