AU615455B2 - Electrical control apparatus - Google Patents

Description

AU-AI-19445/ 8 8 WOCT WORL TE PR ERTI GA TON P C T In L n 'i rea INTERNATIONAL APPLICATION PFLLIS ED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classification 4 (11) International Publication Number: WO 88/ 10020 H02J 13/00, H05B 37/02 Al (43) International Publication Date: December 1988 (15.12.88) (21) International Application Number: PCT/AU88/00183 (74) Agent: COWIE, THOMSON CARTER; 71 Queens Road, Melbourne, VIC 3004 (AU).

(22) Iternational Filing Date: 10 June 1988 (10.06.88) (81) Designated States: AT, AT (European patent), AU, BB, (31) Priority Application Number: PI 2434 BE (European patent) 1G, BJ (OAPI patent), BR, CF (OAPI patent), CG .OAPI patent), CH, CH (Eu- (32) Priority Date: 12 June 1987 (12.06.87) ropean patent), CM (OAPI patent), DE, DE (European patent), DK, FI, FR (European patent), GA (33) Priority Country: AU (OAPI patent), GB, GB (European patent), HU, IT (European patent), JP, KP, KR, LK, LU, LU (European patent), MC, MG, ML (OAPI patent), MR (OA- (71) Applicant (for all designated States except US): STA- PI patent), MW, NL, NL (European patent), NO, REC NOMINEES PTY. LTD. [AU/AU]; 6 Barrie RO, SD, SE, SE (European patent), SN (OAPI pa- Road, Tullamarine, VIC 3043 tent), SU, TD (OAPI patent), TG (OAPI patent), US.

(72) Inventors; and Q.J.P. 9 MAR 1989 Inventors/Applicants (for US only) STAREC, Mario Published [AU/AU]; 73 Augustine Terrace, Glenroy, VIC 3046 With international search report.

STAREC, Rado [AU/AU]; Lot 3, St. Johns Road, Bulla, VIC 3047 HOLA, Jan [AU/AU]; 51 Forest Park Road, Upwey, VIC 3158 AUSTRALIAN 4 JAN i989 PATENT OFFICE (54) Title: ELECTRICAL CONTROL APPARATUS (57) Abstract A low voltage control system for high voltage electrical circuits (32) has a controller (12) incorporating a microprocessor (21) to which is connected a plurality of switching devices (16, 34). Each switching drvice (16, 34), when actuated, results in an input signal to the microprocessor (21) which identifies the initiating switching device (16, 34). An output signal ig generated by the microprocessor (21) in accordance with a programmed instruction set, the output signal being directed to a predetermined circuit controlling relay device (19, 33, 39) to cause switching or control of the designated high voltage circuit (32) which is associated with the actuated switch device (16, 34). A switch device (16, 34) can control one, or any number of circuits depending on its defined function.

i ,r WO 88/10020 P CT/A U88/00 183 -1- ELECTRICAL CONTROL APPARATUS Field of the Invention This invention relates to electrical control apparatus and relates particularly to electronic switching using low voltage switching circuits to control higher voltage electrical or electronic componentry.

The invention is applic ble to any electrical switching circuit and may have particular applicability to switching circuits for controlling lights in buildings, electric motors, heaters, electrical equipment in domestic situations and the like. For convenience, the invention will be described herein with regard to the control of light circuits operating on a normal 240 volt A.C. supply.

It will be appreciated, however, that the principles of the invention are applicable to any electrical switching or controlling situation.

Background of the Invention To control lights in, for example, an office building, it is usual for each individual light or for groups of lights in 'specific locations to be controlled by one or more switches connected to the lights by switching cable carrying full oltage. In some cases, the lights may be connected through a timer so as to be switched on and off automatically. In other cases, 2-way, 3-way or even 4-way switching may be provided to enable the lights to be controlled from a number of switching points.

Such multiple controlling points require substantial cabling to extend between each switch and the lights to be controlled.

In many instances, specially constructed partitioning channels are required to house the cable, and special switches* are required to ensure that there is no danger to the user of the equipment. Further, cables must be run and supported in such a fashion as to comply with wiring requirements which are prescribed to ensure maximum safety.

The above provisions, therefore, result in relatively high wiring costs and high costs of associated WO 88/10020 PCT/AU88/00183 -2building structures, such as the office partitions and the like.

In some situations, it is desirable that, for maximum convenience, safety and for aesthetic purposes, a switch location be provided on a glass panel or partition, on a window or in a similar location. Heretofore, it has not been possible to provide such a switch location without mounting an aesthetically undesirable mounting box and installing high voltage cable to the switch in aesthetically unattractive conduit or the like.

Background Art Australian Patent Application No. 30261/84 Sociedad Espanole De Construcciones Electricas, S.A. filed July 4, 1984 discloses an electronic system for automatic control of electric circuits, including lighting circuits and the like. The system disclosed includes a programming module having a keyboard through which data can be introduced, a display and an interface driver for the display to connect with a basic module. The basic module has a microprocessor, including a central processing unit with random access memory and a ROM which contains programs for operation .of the system. A time base controlled by a crystal provides clock functions, and i a. output of the microprocessor actuates a control relay in accordance with programming in the ROM or as inputted to the -RAM. Astronomic data is stored by the microprocessor so that the output can control lighting in accordance with astronomic dictates with respect to the date and time.

While the controller is able to be programmed for automatic control of lighting, or other equipment, there i .o provi4sion in this system for the microprocessor to respond to a plurality of individual inputs for control of electrical equipment.

Australian Patent Specification No. 58469/86 filed by Lightolier Incorporated on June 6, 1986 discloses a programmable lighting circuit controller to provide control of a plurality of domestic circuits. The controller

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S WO 88/10020 PC/AU88/00183 -3includes a microprocessor with a programmable memory to receive input data which establishes preset power levels in circuits controlled by the controller. The control means enables selective designation of one of the lighting circuits to be a heater circuit for a further circuit which includes a fluorescent lamp. The controller stores desired lighting levels and has level adjusting means to vary the power to the lighting circuits. When desired, the circuits are automatically adjusted to the preset level.

Such a controller uses the microprocessor for storing lighting levels and enabling levels to be changed or stored as desired. However, the system is relatively limited and does not facilitate variations in switching controls between various lighting circuits.

Accordingly, it is desirable to provide an electrical control apparatus whereby electrical circuits, including lighting circuits, are controlled from desired switching locations, the locations being able to be set or changed as desired.

It is also desirable to provide electrical control apparatus for lights and other electrical equipment utilizing low voltage switching to control the relatively high voltage equipment.

It is also desirable to provide control apparatus which will enable switches to be mounted on glass partitions, windows or in similar locations or to provide surface mounted switches at c6nvenient locations without the need for running high voltage cabling.

It is also desirable, in many electrical installations, to have lighting and other apparatus controlled by one oi more timers so that lights, or other equipment, are automatically switched on and off at desired times.

Further, it is desirable to provide means for enabling lights to be automatically dimmed, but not extinguished, so as to reduce power consumption during periods of time when the lights are used solely for security or safety purposes.

-4- Thus, it is desirable to provide apparatus which provides versatile control of electrical circuits.

Summary of the Invention Objects and other advantages of the present invention will become apparent from the following description. According to one aspect of the invention there is provided a low voltage switching or control system for switching or control of electrical apparatus operating at a higher voltage, such as 110 volts or 220 volts, comprising a microprocessor having a pre-programmed instruction set, a plurality of input signal means some of which are switch means, a plurality of output means for the high voltage circuits to be controlled, low voltage circuit means for each input signal means interacting with low voltage circuit means for other input signal means to provide a number of signal paths to the microprocessor less than the number of input signal means, the signal paths providing signals identifying individual input signal means, and the microprocessor polling said signal paths and receiving input signals from the input signal means and giving rise to output signals in accordance o with the pre-programmed instruction set, the output signals being directed by the input signal means and the instruction set, and each output means comprising a low voltage to high voltage relay means associated with each high voltage circuit and operable by the output signals to switch or control the respective high voltage circuit in accordance with the input signal received.

For the purposes of this invention, the term "low voltage" will be used to refer to voltage levels below about 60 volts and the term "high voltage" will be used to refer to voltage levels above that figure.

In a preferred form of the invention, the microprocessor is connected to a plurality of low voltage circuit switches which control a plurality of high voltage electrical circuits. The microprocessor is programmed to identify the appropriate input control signal and to send the appropriate output signal to the low voltage/high voltage relay.

Preferably, a checking circuit is provided to constantly monitor the operation of the microprocessor and to reset the system in the event of a momentary failure or the like.

A, L 1.) <NT i N'Tu~S In one form of the invention, the microprocessor uses eight input control signal paths to control up to 16 high voltage electrical circuits. By utilizing this feature of the invention, the cabling or wiring requirements of the low voltage switches are reduced by half that normally required, thus substantially reducing cost and wiring complexity.

In accordance with a further aspect of the invention there is provided a low voltage control system for the switching of a plurality of high voltage electrical circuits comprising a microprocessor incorporating a read only memory, the microprocessor having a plurality of outputs by which control of the circuits is effected, a plurality of individually identifiable circuit controllers to receive output signals from said microprocessor outputs and distribute them to the appropriate circuit, a plurality of individually identifiable command controllers, each command controller connected to a plurality of input signal means actuatable to give rise to an input signal to switch or control one or more of the high voltage electrical circuits, said input signal being passed to the microprocessor to thereby generate an output control signal, the memory of the microprocessor storing an instruction set which is followed by the microprocessor to continuously poll the command controllers to identify an input signal and to generate an appropriate output signal to switch or control the appropriate high voltage circuit associated with the actuated command controller.

In one form of this aspect of the invention, the command controllers include switching means and electronic circuitry which enables a particular switching means to be identified. The switching means identity is transmitted to the microprocessor S which effects operation of the appropriate output controlled by that switching means under the program means.

A plurality of microprocessors may be interconnected to form an integrated system for the control of a large number of electrical circuits by at least an equivalent number of electrical switching devices. Such switching devices are connected to command controllers which, themselves, may incorporate a switching device.

With this arrangement, the microprocessor outputs are directed to a number of circuit controllers each of which effects control of a number of electrical circuits. The microprocessor incorporates a read only memory, preferably a random access memory, a real time clock and, preferably, a number of communication ports which enable the L1 5A microprocessor to be interconnected with a printer, a video display unit, a modem and/or automatic telephone dialer. A keyboard may also be connected to the microprocessor to facilitate programming or re-programming of the unit.

In order that the invention will be more readily understood, an embodiment thereof will now be described *ee :4 eai

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L NVOo 88/10020 PCT/AU88/001 83 -6with reference to the accompanying drawings.

Description of the Drawings Figure 1 is a block diagram illustrating components of the invention, Figure 2 is a circuit schematic showing the circuit component connections of the first embodiment of the invention, Figure 3 is a block diagram illustrating a second embodiment of the invention, and Figure 4 is a further block diagram illustrating a third embodiment.

Description of the Preferred Embodiments Referring to Figures 1 and 2 of the drawings, the control apparatus of the invention incorporates a controller 12 which receives a low voltage power supply from the power supply 14 to control a number of high voltage switched circuits 17 in response to operation of low voltage switches 16. The high voltage switched circuits 17 are controlled by relay switches 19, the switehed circuits .1 receiving high voltage power from distribution box 18.

The switches 16 illustrated may comprise membrane switches which are able to be mounted at any desired location, including on glass such as glass partitions, windows, doors and the like. The membrane switches 16 require. a light touch only to actuate the electrical circuit. Fine, low voltage wiring is used to connect the membrane switches 16 to the controller 12, such wiring being virtually unseen on glass, thus making the membrane switches ideal for control of lighting circuits in offices and the like which utilize glass walls, glass partitions.

and the like.

Referring to Figure 2, the controller 12 incorporates a microprocessor 21, such as an MC68705P3 which is a commercially available microprocessor. The microprocessor 21 is programmed to control each of the high voltage circuits 17 in accordance with a desired control operation subject to actuation of the relevant membrane WO 88/10020 PCT/AU88/00183 -7switch 16. Thus, actuation of one of the membrane switches 16 may result in a light being switched on. Actuation of another of the membrane switches may result in a plurality of lights being switched off. Actuation of still further one of the membrane switches may result in all lights in an area being switched to an on condition, including lights previously switched off.

The microprocessor 21 may also be programmed so as to automatically control operation of lights, motors, heaters or any other electrical apparatus in accordance with a timing circuit. Thus, lights can be switched on and off periodically, or in a desired sequence or at predetermined times. Where the low voltage to high voltage relay means comprises a triac-controlled switch, or other controllable switch, the intensity of the lights may also be varied as desired by controlling the operation of the triac or other switch circuit.

It will be seen, therefore, that the programming of the microprocessor can be varied to take account of any desired switching function or control function having either a timed operating parameter or operable by actuation of an external, low voltage switch, such as a membrane switch.

As shown in Figure 2, sixteen switches 16 are connected by only eight conductors 22 to the microprocessor 21. The conductors 22 interconnect groups of the switches 16 in such a manner that each switch has two conductors while no one switch has the same two conductors. A bidirectional buffer 10 in each conductor path 22 enables the microprocessor to periodically interrogate the inputs A0 to A7 to determine if a change of state of any of the switches' 16 has taken place. The combination of inputs affected by the change of state indicates to the microprocessor 21 which, if any, of the sixteen switches 16 has been actuated. The microprocessor 21 will then cause an output signal to pass to the appropriate relay switch 19 to actuate the circuit controlled by that actuated switch.

S WO 88/10020 PCT/AU88/00183 -8- The microprocessor operates at 12 volts D.C. to provide a safe operating voltage within the control circuit j switches. The switch wiring allows connection of control i switches around an installation area such that each switch i 5 may be arranged to control a single function or several j switches may be arranged to control the one function, such as in the case of 2-way, 3-way, and 4-way controlled lights. Similarly, one switch may be designated a master j on/off switch while other switches may be used to control i 10 lights of designated areas with still further switches j within those areas to individually control lights therein.

All such control functions are possible by suitable programming of the microprocessor to pass an output signal to the desired low voltage/high voltage relay means on 15 receipt of signals from predetermined switches 16.

Although reference is made to low voltage/high voltage relay means, it will be appreciated that the output signal from the microprocessor 21 can be used in any suitable fashion as a switching or control signal. As previously indicated, the output signal may be used to control the dimming function on a light, or to provide variable control for any other electrical equipment.

If desired, the microprocessor may be programmed to send coded signals for various control functions.

The microprocessor 21 incorporates various inputs for alarm monitoring circuits 26, real time clock circuit 27, etc. as well as outputs such as alarm output circuit 28.

Referring to Figure 3, in this embodiment the ontroller 12, which incorporates a microprocessor, controls the operation of up to sixteen electrical circuits 32, which may be lighting circuits, heating circuits or the like. Each circuit 32 is a high voltage circuit controlled through a low voltage/high voltage relay 33 which interfaces the circuit 32 with the controller 12.

Each of the individual electrical circuits. 32 is controlled by one or more switching devices 34 associated with one or more command controllers 36. The WO 88/10020 PCT/AU88/00183 -9command controllers 36 include circuitry which detects the closure/opening of the switching devices 34, whether those switching devices be momentary closure devices or positive switches. Each command controller 36 has an inbuilt identification code and the microprocessor in the controller 12 continuously polls the command controllers 36 to ascertain if there is any change of state in any of the swtiching devices 34. When a change of state is detected, the command controller 36 is able to indicate to the microprocessor which of its associated switching devices 34 has been actuated. The microprocessor then determines which of the output circuits is to be varied in accordance with the switch actuation so that the appropriate electrical circuit 32 is switched, or controlled.

Switching may consist of ON/OFF switching whereby lights, heaters, motors or the like are connected and/or disconnected from the supply. Alternatively, the switching may comprise a variable switching. With this arrangement, a single pulse from a switching device 34 will vary the output from the controller 12 by a predetermined amount, the relay 33 including cirrent/voltage control circuitry such as a triac controlled circuit, whereby the variation in the output from the controller 12 causes a predetermined reduction/increase in power supplied to the circuit 32.

With this arrangement, by maintaining a switching device 34 in an actuated condition, a series of output pulses may be provided from the controller 12 to cause the electrical circuit 32 to be varied between a low power level and a high power level. A single actuation of the switching device 34 may, subject to the programming of the microprocessor, result in the electrical circuit 32 being switched to a predetermined power level, that power level including fully off and fully on.

It will be seen, therefore, that the microprocessor in the controller 12 can be programmed to continuously poll the command controllers 36 to ascertain the state of any switching devices 34 connected thereto and to WO 88/10020 PCT/AU88/00183 provide an output to a relay to actuate that relay in accordance with a pre-programmed response dependent on the actuation of the switching device 34.

In the embodiment illustrated in Figure 3, the controller 12 has a maximum of 16 output circuits and i the combination of switching devices 34 has a maximum of 16 input combinations. Thus, several of the switching devices 34 illustrated in Figure 3 will perform the same i function for at least one of the electrical circuits 32.

i 10 The information transmitted between the command controllers 36 and the controller 12 is in the form of digital information. The command controllers 36 will include a buffer to store signal information until the microprocessor in the controller 12 is able to extract or respond to that stored signal.

While Figure 3 shows the command controllers 36 in a loop, it will be appreciated that the command controllers may be connected to the controller 12 in a multidrop configuration or as separate inputs.

A feature of the system of the invention is the Suse of a four wire communication configuration in the connecting circuitry of the loop which interconnects the command controllers 36. The four wires permit up to sixteen command controllers connected in a single loop.

It will be appreciated that radio or infrared signals. mnay also be used to interconnect command controllers 36 with the controller 12, in a known manner..

With the embodiment of the invention in Figure 3, the controller 12 has its outputs directly controlling the electrical circuits 32. As previously indicated, -4up to 16 circuits may be controlled from a single controller 12.

Referring to Figure 4, a further embodiment of the invention is illustrated in which the controller 12, incorporating the microprocessor, has a number of command controller loops 37 and provides outputs 38 to a plurality of circuit controllers 39. In the embodiment illustrated, up to 32 circuit controllers 39 are provided and each

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1 i WO 88/10020 PCT/,,U88/00183 circuit controller 39 is able to control up to sixteen separate electrical circuits 32. As will be appreciated, the number of separate electrical circuits 32 able to be controlled from an individual controller 12 depends on the type of microprocessor utilized.

In this embodiment, four command controller loops 37 are provided, each loop incorporating up to 16 command controllers and each command controller is able to monitor up to nine individual switching devices 34. Thus, up to 576 individual switching operations is able to be monitored by the microprocessor and as a result of such monitoring any one of the 576 electrical circuits 32 controlled through the circuit controllers 39 can be actuated, or varied, in accordance with the progrm control of the microprocessor.

As indicated previously, each of the .command controllers 36 in each of the loops 37 is polled by the microprocessor to ascertain any change of state of any of the command controllers 36 which may have occurred due to any one of the associated nine switching devices having been actuated. If the polled command controller 36 gives a positive response to the poll, such response will ind.4cate which of its associated switching devices 34 has been actuated. The microprocessor, having been pre-programmed with data concerning each of the switching devices .34, can identify the particular device which has been actuated and provide an output to the appropriate electrical circuit 32 which, according to the program, is controlled by that actuated switching device 34.

In addition, the microprocessor can ascertain from the command controller 36 the nature of actuation of the switching device 34. Thus, if there has been a single, momentary actuation, the microprocessor can provide the appropriate signal to the electrical circuit 32 in accordance with the programmed information whereby that electrical circuit 32 will be controlled as required.

Thus, a single application may turn OFF or turn ON the circuit, or may vary a light intensity by a predetermined WO 88/10020 -12- PCT/AU88/OO 183 amount, or may vary a heater control or have any other desired, pre-programmed response.

If the microprocessor detects that the switching device 34 has been continuously operated over a predeterminined period of time, a variation on the single to the appropriate electrical circuit 32 can cause a variation in that circuit as appropriate to the sensed input.

In other words, if a light switch is momentarily actuated, the light may be switched on, or off, depending on its previous state. Continuous actuation of the light switch, however, may cause the light intensity to be varied either up or down so as to cause the light to become dim or brighter. The programming associated with the microprocessor is able take account of the time of operation of the switching device 34 and appropriatly control the electrical circuit 32 accordingly.

As indicated previously, some of the switching devices 34 may be designated as main control switches whereby actuation effects a number of the outputs 38 to thereby control a number of the electrical circuits .32.

The microprocessor may be programmed so that any switch actuation can result in any desired operation of any one or more of the electrical circuits.

In addition, the microprocessor may be programmed so as to provide time related operations for at least some of.the electrical circuits 32. Such operations may be associated with security lighting, which is automatically switched on at appropriate times, emergency lighting which is automatically switched on in the event of a major power failure, alarm system operations controlled through alarm sensors interconnected through the microprocessor and having outputs connected to alarm systems, and any other appropriate warning device which may be associated with the operation of electrical systems.

As shown in chain dotted lines in Figure 4, a plurality of controllers 12 may be interconnected so that actuation of a switching device 34 associated with one controller 12 will cause actuation of electrical circuits

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"WO 88/10020 PCT/AU8/00183 -13- 32 associated with a further controller 12a interconnected with the controller 12. Up to 64 controllers 12 may be interconnected in such a manner so that the command controllers of each are able to be utilized to control electrical circuits associated with adjacent controllers.

Further, a system of interconnected controllers 12, termed a floor controller, may be interconnected using a level controller with another floor controller. In this way, a building system may be interconnected using floor controllers to interconnect all the controllers 12 on a single floor level and each level is interconnected using a level controller to control each floor level.

A main controller comprising a micro or mini-computer connects with one of the level controllers to thereby collate all the information within a complex and allowing an operator to view, modify, reprogram and display information on any of the devices connected to any of the level and floor controllers.

Any pf the normal computer input and output ports may be utilized for video display, keyboard input, technician maintenance interrogation and the li.e, as is known in the art.

Similarly, as shown in Figure 4, each controller 12 may be provided with input and output ports to which may be connected a printer 42, an alarm input 43 and alarm output .44, a keypad 46 to enable individual controllers 12 to be programmed or re-programmed and a VDU display.

Claims (18)

1. A low voltage switching and control system to switch and control a plurality of higher voltage electrical circuits, comprising a microprocessor having a pre- programmed instruction set, a plurality of input signal means some of which are switch means, a plurality of output means for the high voltage circuits to be controlled, low voltage circuit means for each input signal means interacting with low voltage circuit means for other input signal means to provide a number of signal paths to the microprocessor less than the number of input signal means, the signal paths providing signals identifying individual input signal means, and the microprocessor polling said signal paths and receiving input signals from the input signal means and giving rise to output signals in accordance with the pre-programmed instruction set, the output signals being directed by the microprocessor to predetermined high voltage circuits in accordance with the identified input signal means and the instruction set, and each output means comprising a low voltage to high voltage relay means 15 associated with each high voltage circuit and operable by the output signals to switch or control the respective high voltage circuit in accordance with the input signal received.

2. A system according to claim 1 wherein the microprocessor instruction set gives rise to predetermined output signals for automatic operation of at least some of the circuits without corresponding input signals. S"

3. A system according to claim 1 or claim 2 wherein input signals of different durations are detected by the microprocessor and result in output signals having .:o different control functions for the respective circuit.

4. A system according to any one of claims 1 to 3 wherein the relay means comprises a circuit ON/OFF switch and a variable voltage/current control to vary the power in the high voltage circuit in accordance with a predetermined output signal.

A system according to any one of claims 1 to 4 wherein the signal means comprises switches connected to the microprocessor through a circuit incorporating buffer means, the switches being connected across a plurality of wires, the number of nS 1 'C! C. I I I i wires being related to the number of switches by the formula: y-2/x where y number of wires x number of switches and each switch is connected across different wire pairs whereby the identification of an actuated switch is effected by identifying the wire pairs.

6. A system according to claim 1 wherein the microprocessor includes inputs and outputs for alarm detection and actuation, keypad input and VDU display output.

7. A system according to claim 1 or claim 6 wherein a plurality of microprocessors are interconnected and programmed to inter-act whereby an input to one microprocessor gives rise to an output signal from another microprocessor.

8. A system according to claim 1, wherein said input signal means comprise command controllers which either incorporate switch means or have a plurality of S switch means associated therewith, a plurality of said command controllers being connected in an input circuit loop or circuit drop with the microprocessor, and the o microprocessor being programmed to periodically check each command controller to detect actuation of one of the switch means, each command controller being g independently identifiable by the microprocessor and each switch means associated with the rzspective command controllers also being independently identifiable. 1i20

9. A system according to claim 8 wherein up to four inpwt circuit loops are connected with the microprocessor, each loop having up to sixteen command controllers and each command controller controlling up to nine switch means.

A system according to claim 8 or claim 9 wherein output signals from the microprocessor are directed to circuit controllers each of which controls a plurality of the high voltage circuits through said plurality of relay means, the circuit controllers operable in accordance with the output signal to direct the output signals to the appropriate relay means to effect switching or control of the desired circuit or circuits.

11. A system according to claim 10 wherein up to 32 circuit controllers are connected to the microprocessor and each circuit controller is connected with up to sixteen high voltage circuits.

12. A system according to any one of claims 6 to 11 wherein said microprocessor g: -16- has an expansion interface whereby a main computer is able to communicate instructions to any one of a plurality of interconnected microprocessors and is able to control, change, log and report on the system operation.

13. A low voltage control system for the switching or control of a plurality of high voltage electrical circuits comprising a microprocessor incorporating a read only memory, the microprocessor having a plurality of outputs by which control of the circuits is effected, a plurality of individually identifiable circuit controllers to receive output signals from said microprocessor outputs and distribute them to the appropriate circuit, a plurality of individually identifiable command controllers, each command controller connected to a plurality of input signal means actuatable to give rise to an input signal to switch or control one or more of the high voltage electrical circuits, said input signal being passed to the microprocessor thereby to generate an output control signal, the memory of the microprocessor storing an instruction set which is followed by the microprocessor to continuously poll the command controllers to identify an input signal and to generate an appropriate output signal to switch or control the appropriate high voltage circuit associated with the actuated command controller.

14. A system according to claim 13 wherein the output signal generated by the microprocessor is specific to actuation of a given input signal means whereby each input signal means is separately operable to switch or control either separate high voltage circuits or separate combinations of such circuits.

A system according to claim 13 wherein the instruction set includes time-based i instructions which generate output signals for switching or control of circuit as a j function of time and/or time elapse without input signals from the command 25 controllers.

16. A system according to any one of claims 13 to 15 wherein signal transmission between command controllers, interconnected microprocessors and circuit controllers is by hard wire, radio, laser,optical cable or infrared transmission.

17. A system according to any one of claims 13 to 16 wherein the switching or control of the high voltage circuit includes ON/OFF switching and circuit power variation for light dimming, and the duration of an input signal determines the control function. 1C,1 i i P i 2 -I 17-

18. A low voltage switching or control system substantially as hereinbefore described with reference to any one or more of the accompanying drawings. DATED this 9th day of July, 1991. STAREC NOMINEES PTY. LTD. 0 9 *c S.. !wtr