GB2291993A - Remote monitoring and signalling - Google Patents

Abstract

For the remote monitoring of electrical apparatus (11, 12, 13) the mains power supply (19, 20, 21) is used to transmit signals from the apparatus to a controlling station (17). Local processing (14, 30) is provided at the apparatus to reduce the amount of data to be transmitted and allow the user to program what parameter(s) it is desired to monitor. Signals imposed onto the mains are at a much higher frequency than the mains supply. An address code unit (34), with breakable wires to set the address, plugs into each local unit (14). To avoid signal conflict, each local unit (14) asks permission to transmit. <IMAGE>

Description

IMPROVEMENTS IN AND RELATING TO REMOTE MONITORING AND SIGNALLING This invention relates to improvements in and relating to remote monitoring and signalling, especially (but not exclusively) to improvements relating to mains signalling to monitor electrical appliances such as street furniture.

It has been proposed to monitor the operation of lamp posts remotely using signals carried by the power supply cables that feed power to the lamp posts. In its simplest form information relating to a particular parameter is sent down power supply cables to a remote processor unit. The unit processes the information and produces data which may be accessed by a viewer or operator and analysed. However, if a hundred lamposts are on one power supply line and each of them is continuously sending signals to the remote processor unit there will be a lot of signal traffic on the power supply line. A high density of data traffic and noise on the supply line can cause corruption of the signals, which makes signal reading and analysis difficult for the remote processor unit.

According to a first aspect of the invention we provide a method of remote monitoring of an electrical apparatus, the method comprising providing a sensor to monitor a parameter of the electrical apparatus, providing a remote unit geographically separate from the electrical apparatus, at which a user can obtain information about the electrical apparatus and further comprising providing a local processing unit at the electrical apparatus, the processing unit processing the signals from the sensor before it transmits its own signals to the remote unit.

The local processing unit receives signals from the sensor and sends out separate signals to the remote unit. It can therefore process the sensor signals itself and does not need to transmit all of the raw, original data over substantial distances. This means that the sensor signals should be less corrupted and less noisy before they are processed by the local processor. Furthermore, the local processor may send its signals to the remote unit only at certain times, for example when the remote unit is not being addressed by any other remote local processor, or at regular intervals, for example every hour or once a day. The local processor may poll the remote unit periodically and transmit its processed data signals only when it receives back a down loading signal.There is therefore no need to have continuous polling of the local processor because it can process signals and store relevant data, for example statistical data, locally.

The local processor may be arranged so that it monitors signals from the sensor continuously or at predetermined times. The local processor may only store data on signals if predetermined criteria are met. The local processor may filter out a lot of data and not transmit information relating to all sensor signals to the remote unit. For example, in lamp posts most lamp failures occur in the first 30 minutes following start up of the lamp. The local processor may record data indicative of the performance of a lamp post unit for only a predetermined time (eg 30 minutes) following start up of the lamp . Alternatively, or additionally, the local processor may monitor sensor signals, but not record data on them (for onward transmission to the remote unit) unless they fall outside (or within) a predetermined range or value.For example, a lamp post has a normal operating state. The local sensor could be set up to ignore signals that are at the normal level, or within an allowable deviation of "normal".

If the sensor was looking at the voltage across a particular resistor in the lamp post it might ignore signals that are within the range of, say, 5V +0.5V (a 20% band of tolerance). If signals fall outside of an allowable range the local processor records information relating to them and in due course sends signals to the remote unit. Instead of waiting for its normal polling time the local unit may be set up to poll the remote unit as soon as an unacceptable signal has been received, or when it determines that the out-of-range sensor signal is not an error. The local processor preferably processes a plurality of sensor signals that it receives and dependant upon these sensor signals the local processor preferably passes on appropriate signals to the remote unit. Preferably the local processor processes a plurality of different physical parameters.For example it may receive and process: a) signals indication of voltage at one point; or b) voltage at a second point; or c) current at a point; or d) temperature; or e) stress or any other parameter; or f) any combination of a) to f).

According to a second aspect of the invention we provide monitoring apparatus for monitoring electrical apparatus comprising a sensor to monitor a parameter of the electrical apparatus, a local processing unit and a remote unit geographically separate from the electrical apparatus in which the local processing unit is adapted to process signals from the sensor and transmit its own signals to the remote unit.

The remote unit may be interrogated by a user.

According to a third aspect of the invention we provide a kit for assembly into monitoring apparatus for monitoring electrical apparatus comprising a sensor, a local processing unit and a remote unit.

Noise rejection is a problem when signals are transmitted from local processors to the remote unit.

Transmitting information only periodically, instead of continuously reduces the likelihood of interference between signals from different local processors.

Similarly, transmitting only when the remote unit indicates that there is no other signal traffic reduces noise.

According to a fourth aspect, the invention comprises transmitting a data carrier signal from the local unit to the remote unit, the carrier signal being at a substantially higher frequency than the frequency of the mains supply.

According to a fifth aspect of the invention we provide an apparatus for transmitting a data carrier signal along a mains supply line in which the apparatus is adapted to transmit a carrier signal at a frequency substantially higher than the frequency of the mains supply.

Most noise is at or around the mains frequency.

We may transmit a carrier signal from a local processor to a remote unit in the KHz range, preferably at least 50 KHz.

We may provide the local unit with the facility to adjust the carrier frequency. In one embodiment the mains carrier frequency is adjustable from 5-125 KHz in accordance with regulatory requirements.

According to a sixth aspect of the invention we provide monitoring apparatus adapted to monitor the operation of an electrical device or installation, the monitoring apparatus comprising a sensor adapted to produce signals, indicative of a physical parameter, and processing means adapted to process the signals and emit signals of its own characterised in that the processing means comprises a microcontroller.

According to a seventh aspect of the invention we provide a method of monitoring the operation of an electrical device or installation comprising the steps of measuring a physical parameter of the electrical device with a sensor and processing signals provided by the sensor with a microcontroller.

According to an eighth aspect of the invention we provide a kit for assembly into a monitoring apparatus adapted to monitor the operation of an electrical device or installation, the kit comprising a sensor adapted to produce signals and processing means in which the processing means comprises a microcontroller.

Preferably the monitoring apparatus is street furniture monitoring apparatus. Hitherto, even if local processing had been thought of there would be a prejudice against using a microcontroller in the local units. A street having 100 lamp posts might, in one preferred arrangement, have each lamp post provided with its own local processor, or small groups of lamp posts may be provided with a shared local processor.

Thus up to 100 local processors are needed.

Microcontrollers are very expensive to design, and even when designed are much more expensive than microprocessor chips.

We have surprisingly found that it does make sense to use a microcontroller, despite the initial prejudice against doing so. Even though they cost much more than microprocessor chips they are much better at data logging and local processing. The advantages of reduced data traffic to the remote unit and less noise can most surprisingly outweigh their cost.

In one preferred embodiment a substantial part of the invention resides on the realisation that the cost of manufacturing a local controller, which has a microcontroller can be drastically reduced if we use a microcontroller that has already been designed for one purpose and reconfigure it, with appropriate other electrical components, to adapt it to monitor the electrical device we have in mind. This could be a lamp post, or any other item of street furniture. It could even monitor assemblies that are not street furniture.

For example, it could monitor the power uptake of a domestic dwelling and thereby effectively be a local meter which can send meter reading signals to a remote unit.

Preferably the microcontroller is provided encased in a matrix, such as a resin block. This protects the assembly of the microcontroller and associated conversion circuitry. Hitherto it has been unthinkable in such a high volume product as a monitor or a control unit for street furniture to encase a microcontroller assembly in a protective matrix. If anything goes wrong with the associated, and cheap, electronics which accompanies a microprocessor chip it is conventional to take the board upon which the microcontroller and associated circuitry are mounted out of the apparatus and see if the board can be repaired. By encasing the assembly in a matrix there is no possibility of repair. This means that a F2-3 microcontroller could be made useless by the failure of a 1 penny resistor.

Up until now this has meant that microcontrollers, at least in high volume, cost conscious, products have not been encapsulated in resin. By using commercially available microcontrollers they can be disposable.

Indeed, another way of looking at this aspect of the invention is as a one-slot disposable monitor assembly that incorporates a microcontroller and associated electronic circuitry encased in a matrix, adapted to monitor and process signals from an electrical apparatus.

By having a microcontroller, instead of a microprocessor we can make our monitoring apparatus far smaller than would otherwise be the case. We can therefore retro-fit the monitors/controllers to existing apparatus easily. Alternatively, the monitor may be fitted as a new installation. Another problem associated with monitoring of a large number of electrical devices, such as lamp posts, is that the end user needs to know which unit is showing a problem (so that he can send someone to repair the device). Each device (or group of devices) therefore needs to indicate its own identity. Conventionally this is done by having a slightly differently encoded microchip for each local monitoring device. The local monitoring unit associated with each lamp post codes its signals so that the remote can identify it, and knows to which lamp post the signals relate.This is all very well until the microchip in a local monitor fails. In order to replace the microchips the engineer must contact the manufacturers of the microchips, give them the identity code of the broken microchip and ask them to encode, on a one-off basis, another microchip with the same identity code (so that the remote processor will still associate the signals with the correct lamp post). The engineer must then wait for the replacement part to arrive and then go out and fit it. Thus the engineer usually makes two trips to the lamp post (one to determine that it is the chip that is at fault and a second to fit the replacement chip) and typically has to wait three weeks or so for the replacement chip to arrive.

According to a ninth aspect the invention comprises a method of reducing the down time of a monitor unit for an electrical device, or of reducing the cost of repairing a monitor unit for an electrical device, or of doing both, comprising providing the monitor unit as an operative assembly and an identity code unit, the arrangement being such that the identity code unit can be removed from the operative assembly and can be re-used with a new operative assembly.

This enables us to make all of the operative assemblies of our monitor units identical, without the need to give them an identity code. This reduces their unit cost. Furthermore, since the operative assemblies are identical if one fails on-site an engineer can carry a spare operative assembly with him to the electrical device and can replace it there and then taking out the identity code unit from the old monitor unit and attaching it to the new operative assembly so as to create a new monitor unit, but with the same code unit.

According to a tenth aspect of the invention we provide a monitor unit for an electrical apparatus, the monitor unit comprising a main operative unit having the monitoring electronics, and an identity code unit attachable to and separable from the operative unit, the identity code unit being adapted to interact with the main operative unit to give the monitor unit an identifying code.

The code may be considered to be a coding key. In an even more preferred arrangement the identity code unit comprises a plurality of coupling members adapted to co-operate with a plurality of complementary coupling members provided on the operative unit, the arrangement being such that when the code unit is mounted on the operative unit electrical connection is made between certain complementary coupling members, dependant upon the configuration of the code unit.

Accoding to an eleventh aspect of the invention we provide a kit for assembly into a monitor unit for electrical apparatus, the kit comprising a main operative unit have monitoring electronics and an identity code unit.

Instead of requiring electrical connection to provide the code any suitable interaction may be used (eg, optical coding). The operative unit must simply produce a code signal dependant upon the code unit.

Preferably the code unit has a plurality of wires linking parts of its coupling members. If that is all the electrical content of the code unit there is very little to go wrong with it, which means the engineer will hardly ever have to replace a broken code unit.

In one preferred embodiment the engineer may also carry a spare code unit, or proto-code unit, which can be coded by the user on site, at the vicinity of a broken code unit. Preferably to code the proto-code unit the user makes, or more preferably breaks, one or more connections between pairs of coupling members of the code unit. For example, the proto-code unit may be provided with 8 wires linking 8 pairs of coupling members. The engineer may have a broken code unit which he knows (from his own records) originally had linking wires nos. 1, 6, and 7 broken, and linking wires nos. 2, 3, 4, 5, and 8 intact. He therefore takes the proto-code unit and codes it to the same code as the original code unit by breaking wires 1, 6, and 7 with an appropriate tool such as a small screwdriver.

According to a twelth aspect the invention comprises a method of improving the maintenance of a plurality of electrical devices comprising providing the electrical devices with a local monitor and processor unit adapted to monitor at least one physical parameter and to perform at least some data processing on its input signals indicative of said physical parameter, and a remote unit adapted to receive signals from a plurality of said local units.

According to a thirteenth aspect of the invention we provide an electrical device having a local monitor and processor unit, in which the local monitor and processor unit is connected to a remote unit, and in which said local monitor and processor unit is adapted to monitor at least one physical parameter of the electrical device and is also adapted to process a signal indicative of said parameter and said remote unit is adapted to receive a signal from said local unit.

Preferably the electrical device is an item of street furniture.

The remote unit may be adapted to receive signals from a plurality of said local units.

Preferably the local monitor and processor unit includes a microcontroller. Preferably the microcontroller is embedded in polymer resin or matrix material. Preferably the local monitor processor transmits signals to the remote unit using a high frequency carrier signal. Preferably the local monitor and processor unit has a removable coding unit which is connectable with a base operational unit should the original base operational unit malfunction.Preferably the method further comprises a maintenance engineer visiting an item of street furniture which is detected by the remote unit as malfunctioning, and the maintenance engineer carrying with him a replacement base operational unit and removing the existing base operational unit, removing the code unit from the existing base operational unit, connecting the original code unit to the replacement base operational unit, and connecting the new base operational unit to the item of street furniture.

The maintenance engineer may also carry a spare code unit. He may encode the spare code unit on site, in the vicinity of the item of street furniture, or he may do so remote from the site.

In its broadest aspect the invention (or any aspect thereof) may be considered to relate to a remote metering system, or a process control management system. The system may monitor and/or control a diversity of electrical devices including devices for lighting, heating and humidity or atmosphere control.

This may include lights, heaters, pumps, fans and air conditioning units. The invention is concerned with monitoring the environment (including the operation) of one or more electrical devices and providing data for analysis or changing the operation of the device or devices in response to the environment. Therefore the invention may also be considered as an environmental management system. One application among many possibilities could be in tunnel management. A measurement of temperature or temperature change in the atmosphere of a tunnel can be an indication of CO levels. By monitoring this parameter appropriate activation and control of fans and air conditioning apparatus in the tunnel can be carried out.

Embodiments of the mention will now be described by way of example and with reference to the accompanying drawings of which: Figure 1 shows schematically a system for monitoring and controlling the operation of a number of street lights; Figure 2 indicates schematically a carrier signal at a far higher frequency than noise.

Figure 3 schematically shows a polymer block encapsulating a microcontroller and associated electronics circuiting, and having a demountable identity code key; Figure 4 shows in more detail the identity code key of figure 3; Figure 5 shows a device similar to that of Figure 3, but factory fitted to a cover of a cut-out unit for a lamp post; and Figure 6 shows a monitoring system.

Figure 1 shows three lamp posts 11, 12,and 13.

Each lamp post has its own local processor unit 14, 15 and 16 respectively which monitors the activity of the lamp post and can be used to switch it on and off. A remote unit 17 controls the operation of these local processor units and is shown in dotted outline. It is also shown for greater detail in solid outline in the centre of the page. Power is supplied to the lamp post by a mains supply line 18, and via mains supply lines 17, 18 and 21. The local processor units 14, 15, and 16 signal information back to the main unit 17 by a mains board signalling along the lines 19, 20, and 21.

Telephone line 22 connects the remote unit 17 to a user interface unit 23 which is in a location remote from the remote unit.

The remote unit 17 is housed in a road-side box 24 which is provided with an access door 25. Similarly, each lamp post has an access door to enable an engineer to obtain access to the local processing units.

As shown in Figure 3 each local processing unit 14, 15, 16 comprises a microcontroller 30, an associated conversion circuit 31, and an identifying circuit 32 embedded in the epoxy resin block 33. A variety of input sensors S1, S2, S3 monitor suitable physical characteristics in the electronic circuit of the lamp post, for example S1 might monitor the voltage of a certain point, S2 might monitor the current at a certain point and S3 might monitor the voltage at another point, and so on. The sensors S1, S2 and S3 measure signals sl, s2 and s3 respectively.

The microcontroller 30 is a commercially available microcontroller which is designed for a specific purpose - which is probably other than monitoring a lamp post. However, by an appropriate choice of conversion circuit 31 we can enable the microcontroller 30 to take the input signals sl, s2, s3 and monitor them, instead of those signals which it was originally designed to monitor. For example there are many microcontrollers which are configured to monitor the performance of a vehicle's engine. Thus the functional control circuit 31 is to "fool" the microcontroller into monitoring the signals we want it to monitor.

Microcontroller 30 emits its own report signals back down the power supply line 19, 20, 21, to the remote unit 17. The microcontroller has a memory (not shown) and is programmed by the remote unit 17 to report in a desired way. For example, in this particular embodiment, the remote unit 17 programs the microcontroller so that it records in its memory the performance, at 5 second intervals, of signals sl to s3 for the first 30 minutes of the operation of the lamp post and then stops recording them (because we believe that most lamp failures occur during the first 30 minutes following start up of a lamp). The microcontroller then polls the remote unit 17 to ask for permission to down load its memory to the remote unit 17. If the remote unit 17 sees that there is no other signal traffic then the microcontroller 30 sends out a carrier signal at, say, 100 KHz (schematically shown in Figure 2) and dumps its acquired data to the remote unit 17.

The microcontroller 30 identifies itself by including in the transmitted data an identifying code.

The identifying code is generated by the identifying circuit 32, and relies upon the configuration of a code key 34.

The code key 34, shown in Figure 3, is removable from the resin block 33 and has 16 pins (8 sets of pairs) which are received in complementary holes 36 provided in the resin block. The key 34 is also shown in more detail in figure 4, and has 8 slots 37 in its back to enable a thin tool to be inserted into the slots 37. Behind the slots 37 are, in its original, unencoded state, respective wires 38 linking pairs of pins 35. The key 34 is encoded by breaking, or not breaking, particular wires by pushing the tool through the slots 37. In figure 4 starting from the top, wires 4, 5, and 6 have been broken, leaving wires 1, 2, 3, 5,and 8 intact which provides the key 34 with a binary code (in this example 8 bit). Each local processor unit has its own, individual, and unique, coded key.It will be appreciated with an 8 bit key code we can handle 255 units on a single face conductor. This could easily be upgraded to 1000 units or more simply by adding two or more bits.

It will be appreciated that the keys have a hardware link only, and there is no need to programme the keys at the point of installation.

The individual local processor units 14, 15 and 16 are also programmed by the remote unit 17 to keep a record of any signals which are outside of an allowable range. Although the signals sl to s3 are recorded as a matter of course in the memory of the microcontroller 30 for the first 30 minutes, and not thereafter (as a matter of course), the microcontroller is programmed to monitor the signals continuously (say at 5 second intervals) and to keep a record of signals which are outside of an allowable error band. The microcontroller 30 may also be set up to transmit such unusual signals to the remote unit 17 periodically, or even substantially immediately (when the polling enquiry receives instructions to proceed).

It will be appreciated that the remote unit 17 could be arranged to vary the operational conduct of the microcontroller 30, for example, the user interface 23 could be used to tell the remote unit 17 to change the period of sampling of the signals from once every 5 seconds to once every 10 seconds, or ten times a second, or any other period. Similarly, the initial recording period could be varied.

It will be appreciated that because a microcontroller is a powerful tool it can simply be reprogrammed once by the user interface 23 and then left alone to get on with the job of monitoring/reporting. Because so much processing is done at the local processor unit 14, 15, 16, the volume of signal traffic to the remote unit 17, and to the user interface 23 is kept low, and this avoids confusion between the signals.

It will be appreciated that one of the benefits of the present system is that each of the blocks 33, and each of the microprocessors 30, is identical (or substantially identical). This means that we can mass produce the blocks 33 and use some and store some conveniently. If there is then a problem with one of the blocks 33 an engineer can take a replacement from our store and visit the lamp post that is having trouble (as detected by the remote unit 17, and as interrogated by the user interface 23). He can then simply unplug the key 34, disconnect the broken base unit of the resin block 33 and exchange it for a new base unit resin block 33, and reconnect the same key 34 to the new resin block.This will guarantee that the new resin block will generate the same identity signal (since the identity signal is generated in response to the configuration of the key 34) and the remote unit 17 will be able to correlate incoming signals with a particular lamp post. This avoids the need to have special programming of replacement chips, and reduces the down time involved in maintaining the unit.

In areas where there are special problems, for example in areas near pylons where there may be a lot of interference, we would envisage using special add-on modules to enhance particular performances of the standard resin block 33. For example, we could have a plug-in filter unit to improve the noise filtering.

This may be plugged into special ports in the resin block which when provided in all resin blocks, or may be wired in in-situ.

Similarly, where there is a large distance between the items of street furniture being monitored and the remote unit 17 we could include a booster unit as a separate add-on pack.

Figure 2 also schematically illustrates another feature. The microcontroller can be programmed by the remote unit 17 to adjust the frequency of its carrier signal 40, within a range. The range shown in Figure 2 is 5 kilohertz to 125 kilohertz. In each case, the frequency of the carrier signal is above that of the majority of the noise 41.

One of the advantages of using a microcontroller, as opposed to microprocessors, is that we can have a far more powerful tool in a relatively small space. For example, we would envisage having a resin block 33 roughly 100mm x 55mm x 40mm in size. This is small enough for it to be retrofitted to many items of street furniture, and also to other areas where monitoring the performance for electrical equipment could be used.

One entire field where we think the invention may have applicability is the field of remote metering. The microcontroller could, of course, be set up to monitor the power uptake, and provide signals back to the remote unit 17. Once the power uptake through a particular power line is known then the way forward for remote metering, and automatic billing of consumers for their use of electricity, is open. The system could, in another aspect of the invention, comprise a remote metering system.

Figure 5 illustrates one particular embodiment of the invention. The reader is directed to read contents of a co-pending British Patent Application GB 9325372.2. The contents of that Application are hereby incorporated by reference. As will be appreciated by the skilled person, Figure 5 is very similar to Figure 2 of GB 9325372.2, and shows a view of the inside of a cover for a cut-out unit for street furniture. The cover is referenced 50. A local monitoring unit 51 is attached to the cover 50, and has its identification key 52 shown in the figure. Also shown in the figure in dotted outline, is the possibility of adding a booster unit 53 to enhance the performance of the standard epoxy resin encased unit.

In this particular example the booster unit 53 is a data logger provided to enhance the memory capacity of the local unit so that it can report to the remote unit at intervals.

The unit 53 could, alternatively, be a load switching device adapted to enable the electrical apparatus to which it is connected to be turned on and off remotely. Alternatively, this feature may be provided within the microcontroller.

Figure 6 shows an embodiment of a monitoring system represented in a block diagrammatic form. A computer 62 running the system has dedicated software for data analysis and control. The computer 62 is connected to a monitor 64 by means of a communication link 66. Mains communication buffers 68 and 70 are provided at each end of the link 66. Buffer 68 is connected to the computer 62 by an RS232 or 488 serial link. Buffer 70 is connected to a microcontroller 72 through a decoder 74.

The communication link 66 between the two buffers 68 and 70 is a full duplex link over a mains supply. Information passes along the link 66 to or from the computer 62 on a phase locked loop carrier for data integrity. Transmission can be in a frequency band 5-125 KHz as opposed to the mains which is between 40 to 60 Hz. For further data integrity, an automatic error correction routine is incorporated in the software in the computer 62 to replace any bits of information which are lost. The communication stream between the buffers 68 and 70 can be in a digital form or any other suitable form.

The monitor 64 is provided with an independent power supply 76, which can be a mains supply separate from the main supply providing the link 66.

The microcontroller 72 is fed with information concerning the operation of a piece of street furniture through a number of analogue inputs. We prefer eight analogue inputs although only four inputs 78. 80, 82 and 84 are shown in Figure 6. Each input 78, 80, 82, 84 is provided with a signal conditioner 86 and an opto-isolator 88. The inputs may include signals relating to an A.C. signal (such as mains supply), a D.C. signal, other current signals, or signals representative of absolute temperature or temperature change for example atmospheric temperature or temperature change The signal conditioners 86 scale the signal up or down to be in a range suitable for the micrcontroller 72 to receive. This would be, for example, in the range 0-5V. The opto-isolators 88 provide a potential cut out in case of power surges or other signals which can harm the microcontroller 72.

The microcontroller 72 has at least three outputs.

In the Figure three outputs 90, 92 and 94 are shown.

These may be volt free outputs for external use, pulse width modulation outputs for analogue control of external loads (for example power supply to a lamp) or standard analogue D.C. voltage outputs.

The microcontroller may be provided with a plurality of further input/output ports for monitoring and control as required. In this embodiment two eight bit ports, making sixteen digital input/output ports can be used.

A key 96 (corresponding to key 34 in Figures 3 and 4) shown in the Figure may be plugged into or removed from the microcontroller 72. The key may have an eight or nine bit identity which represents the address of the microcontroller 72.

As has been discussed in the foregoing, the invention is not to be considered to be limited to the field of monitoring street furniture. It may be applied as a metering or control system to a diverse range of electrical devices or apparatus.

Claims (50)

1. A method of remote monitoring of an electrical apparatus, the method comprising providing a sensor to monitor a parameter of the electrical apparatus, providing a remote unit geographically separate from the electrical apparatus, at which a user can obtain information about the electrical apparatus, and further comprising providing a local processing unit at the electrical apparatus, the processing unit processing the signals from the sensor before it transmits its own signals to the remote unit.

2. A method according to claim 1 in which transmission of data between the sensor and the remote unit is not continuous.

3. A method according to claim 2 in which the transmission of data takes place at known or predetermined times or occurrences.

4. A method according to claim 3 in which the transmission of data occurs under fault conditions of the apparatus being monitored.

5. A method according to any preceding claim in which the local processor stores data.

6. A method according to any preceding claim in which selected data is transmitted to the remote unit.

7. A method according to claim 6 in which the reduction in data transfer increases the immunity to noise of the signals transmitted.

8. A method according to any preceding claim in which the local processing unit monitors more than one parameter of the apparatus.

9. Monitoring apparatus for monitoring electrical apparatus comprising a sensor to monitor a parameter of the electrical apparatus, a local processing unit and a remote unit geographically separate from the electrical apparatus in which the local processing unit is adapted to process signals from the sensor and transmit its own signals to the remote unit.

10. A monitoring apparatus according to claim 9 in which the remote unit may be interrogated by a user.

11. A kit for assembly into monitoring apparatus for monitoring electrical apparatus comprising a sensor, a local processing unit and a remote unit.

12. A method of remote monitoring of a device that has a mains supply, the method comprising transmitting a data carrier signal from a local unit to a remote unit, the carrier signal being at a substantially higher frequency than the frequency of a mains supply.

13. Apparatus for transmitting a data carrier signal along a mains supply line in which the apparatus is adapted to transmit a carrier signal at a frequency substantially higher than the frequency of the mains supply.

14. Apparatus according to claim 13 in which the carrier signal from a local processor to a remote unit is in the KHZ range.

15. Apparatus according to claim 14 in which the carrier signal has a frequency of at least 50KHZ.

16. Apparatus according to any of claims 13 to 15 in which the carrier frequency is adjustable.

17. Apparatus according to claim 16 in which the frequency is adjustable in the range 5-125 KHZ.

18. A monitoring apparatus adapted to monitor the operation of an electrical device or installation, the monitoring apparatus comprising a sensor adapted to produce signals, indicative of a physical parameter, and processing means adapted to process the signals and emit signals of its own characterised in that the processing means comprises a microcontroller.

19. A method of monitoring the operation of an electrical device or installation comprising the steps of measuring a physical parameter of the electrical device with a sensor and processing signals provided by the sensor with a microcontroller.

20. A kit for assembly into a monitoring apparatus adapted to monitor the operation of an electrical device or installation, the kit comprising a sensor adapted to produce signals and processing means in which the processing means comprises a microcontroller.

21. A kit according to claim 20 in which a microcontroller designed for a different application has been used in conjunction with conversion circuitry.

22. A kit according to claim 21 in which the microcontroller and associated circuitry is enclosed in a matrix.

23. A kit according to claim 22 in which the matrix is a resin block.

24. A kit according to any of claims 20 to 23 which is adapted to be used in street furniture.

25. A method of reducing the down time of a monitor unit for an electrical device, or of reducing the cost of repairing a monitor unit for an electrical device or of doing both, comprising providing the monitor unit as an operative assembly and an identity code unit, the arrangement being such that the identity code unit can be removed from the operative assembly and can be re-used with a new operative assembly.

26. A method according to claim 25 in which the monitor units produced are identical.

27. A monitor unit for an electrical apparatus, the monitor unit comprising a main operative unit having the monitoring electronics, and an identity code unit attachable to and separable from the operative unit, the identity code unit being adapted to interact with the main operative unit to give the monitor unit an identifying code.

28. A monitor unit according to claim 27 in which the code unit consists of a plurality of coupling members adapted to co-operate with a plurality of complementary members on the operative unit.

29. A monitor unit according to claim 28 in which electrical connection of the complementary coupling members depends on the configuration of the code unit.

30. A monitor unit according to any of claims 27 to 29 in which the code unit comprises wire connections.

31. A monitor unit according to claim 30 in which wires are broken in the code unit as required to produce the correct code.

32. A monitor unit according to any of claims 27 to 31 in which the code unit relies on an interaction other than electrical connection.

33. A monitor unit according to claim 32 in which the code unit uses optical coding.

34. A kit for assembly into a monitor unit for electrical apparatus, the kit comprising a main operative unit having monitoring electronics and an identity code unit.

35. A method of improving the maintenance of a plurality of electrical devices comprising providing the electrical devices with a local monitor and processor unit adapted to monitor at least one physical parameter and to perform at least some data processing on its input signals indicative of said physical parameter, and a remote unit adapted to receive signals from a plurality of said local sources.

36. An electrical device having a local monitor and processor unit, in which the local monitor and processor unit is connected to a remote unit, and in which said local monitor and processor unit is adapted to monitor at least one physical parameter of the electrical device and is also adapted to process a signal indicative of said parameter and said remote unit is adapted to receive a signal from said local unit.

37. An electrical device according to claim 36 in which the remote unit is adapted to receive signals from a plurality of said local units.

38. An electrical device according to either of claims 36 or 37 in which the local monitor includes a microcontroller.

39. An electrical device according to any of claims 36 to 38 in which the processor unit includes a microcontroller.

40. An electrical device according to either of claims 38 or 39 in which the microcontroller is embedded in a polymer resin.

41. An electrical device according to any of claims 36 to 40 in which communication occurs between the local monitor and processor unit using a high frequency carrier signal.

42. An electrical device according to any of claims 36 to 40 in which the local monitor and processing unit contains a removable coding unit.

43. An electrical device according to any of claims 36 to 42 which forms a remote metering system.

44. An electrical device according to any of claims 36 to 43 which forms a process control management system.

45. An electrical device according to either of claims 43 or 44 which connects to a variety of electrical devices.

46. An electrical device according to any of claims 36 to 45 which is designed to interact with the environment.

47. An electrical device according to claim 46 which is adapted to manage the environment of a tunnel.

48. An electrical device according to claim 45 which is adapted to control street furniture.

49. An electrical device substantially as herein described.

50. A method of remote monitoring of an electrical apparatus substantially as herein described.