WO1996018177A1

WO1996018177A1 - Common channel identifying system

Info

Publication number: WO1996018177A1
Application number: PCT/GB1994/002674
Authority: WO
Inventors: Alan Roberts-Carlson; Keith Frederick Roberts
Original assignee: Roberts Carlson Alan; Keith Frederick Roberts
Priority date: 1994-12-06
Filing date: 1994-12-06
Publication date: 1996-06-13
Also published as: AU1246495A

Abstract

The described invention enables communication between nodes on a common channel signalling system without erroneous identification of one device for another. The transmitting device sends an individual code which is learnt by the received equipment and stored in a non-volatile RAM. This sequence is only necessary on initialisation. Subsequent communications use the code known to both devices to distinguish the source of the transmission from another signal similar of structure but different code. Many devices (receivers or transmitters) can use the same channel without mis-operation of any of the devices. The advantage of this system over the traditional method of transmitting one of several determined codes is that the likelihood of coincident settings is reduced to a negligible level. Additionally the end user of the equipment is not required to set up complex codes or work on small electrical switches, which could present problems for the elderly and infirm. The codes used are secret to the systems using them thus avoiding the necessity of remembering code numbers or the security risk of writing them down. It is a simple matter to change the code. The teach/learn system can be re-activated by a couple of switches, thus setting new codes into the system easily.

Description

DESCRIPTION

COMMON CHANNEL IDENTIFYING SYSTEM

The present invention relates to identifying systems, and in particular to identifying systems in which an individual identifying code is assigned to one or more remote communicating devices in order that the source of a signal can be determined and verified.

In accordance with the present invention, there is provided an identifying system comprising a remote unit, a master unit and means for transmitting a signal from the remote unit to the master unit, the remote unit comprising means for unpredictably

generating a number for originating an identifying signal to be associated with the remote unit and transmitting the original identifying signal to the master unit and the master unit comprising means for receiving the initially-transmitted original signal and thereafter recognising the signal, when received subsequently, as originating from the remote unit.

Preferably, the remote unit comprises means for generating a coded signal. The coded signal may be a binary coded signal and may carry information in addition to the code.

The remote unit may comprise means for switching it into a code-originating and transmitting mode and the master unit may comprise means for switching it into a learning mode to store a newly-originated code.

The remote unit may comprise an electronic counter and means for stopping the counter at a number which corresponds to the originating code. The means for stopping the counter may comprise a switch. The system may be arranged so that, subsequent to the transmission of the original identifying signal, actuation of the switch results in the transmission of a test signal.

There may be means for commencing counting by the counter. The counter may be started when the remote unit is switched on.

The remote unit may comprise a random number code generator, preferably an electronic random number code generator. The simple number generated may be further scrambled by an algorithm or a lock-up table technique associated with the remote unit.

There may be a plurality of remote units and/or a plurality of master units. The remote unit and the master unit may communicate in a wire-less manner.

The system may further comprise means for

replacing an existing identifying signal with a new identifying signal.

In one embodiment, the system is in the form of an intruder detection system comprising a plurality of remote units and wherein each remote unit comprises a detector and transmits a signal to the master unit upon activation.

The present invention allows communication between many devices on a common channel without erroneously communicating to other devices. The devices exploiting the invention may be in particular (but not exclusively) devices connected by a common radio, infra red or other medium. The invention embodies special coding techniques which allocate an identifying code to each specific device.

The remote or sending device may typically consist of a transmitter suitable for the medium (such as radio), some hardware logic and an input device such as a manually operated switch, sensor or the like. In addition a power supply such as a battery will be required. The hardware in this invention is capable of generating a code under special

circumstances, such as when the device is powered up, or initialised. This initial code is transmitted from a transmitting device to a receiving device, and subsequently used as a unique identification for the transmitting device. If required the receiving device can instigate a further transmission which is used to signal back to the transmitting device, thus creating a secure two way communication. Transmissions between the devices would usually carry additional information besides the code to indicate a status signal such as the operation of a switch or the state of a battery voltage detected by the logic circuitry. A simple use of this system would be for a radio controlled garage door opener where only the identifying code need be transmitted upon the actuation of a manually operated switch. A more sophisticated use would be in a radio controlled security system where identifying code and status information such as door opening switch and battery level are transmitted as a single message.

The logic can generate the identifying code by several methods, typically by counting the time interval between initial power up and an externally generated event. If the time counter is arranged to count 16 binary bits for example, there would be

65,536 individual possible combinations for the code. The probability of two similar devices which are within communicating range generating the same code is very low. The code generator can use a short or long code depending on the level of security required and is only limited by the amount of logic installed and the length of time available for transmission. This invention has also been developed using a

microprocessor and a time counter implemented in a software algorithm.

By way of example only, specific embodiments of the present invention will now be described, with reference to the accompanying drawings, in which:-

Fig. 1 is a diagram illustrating a first

embodiment of radio-linked security system in

accordance with the present invention;

Fig. 2 is a flow diagram illustrating the setting of an identifying code in the embodiment of Fig. 1;

Fig. 3 is a flow diagram illustrating the

hardware implementation of the code setting shown in Fig. 2;

Fig. 4 is a diagram of a second embodiment of radio-linked security device in accordance with the present invention; and

Fig. 5 is a diagram of a third embodiment of radio-linked security device in accordance with the present invention.

Fig. 1 illustrates the layout of a radio-linked security system comprising a master or base unit 10 and a plurality of remote units 12,14. In the

embodiment illustrates only two remote units are used, but this is done only for the sake of simplicity and one unit or more than two units may be employed. In the embodiment remote unit 12 is shown as comprising a switch 16 for detecting whether a window is open and remote unit 14 is shown as comprising a passive infra-red sensor 18, but these are purely by way of example and other sensors such as pressure pads, magnetic read switches, vibration sensors etc. may be used instead or in addition.

Each of the remote units 12,14 comprises a central processing unit (CPU) 20 and the respective sensor 16,18 communicates with its unit via an

input/output (I/O) interface 22. Each unit 12,14 further comprises an identifying code generator 24, a radio frequency transmitter 26, an antenna 28 and a ROM 29. The CPU 20, the code generator 24 and the transmitter 26 communicate by means of a data bus 30 and the units are powered by a battery (not shown). Each code generator comprises a 16-bit binary counter 32 to which a switch 34 is connected via the I/O interface, for setting the identifying code, as will be explained.

The master or base unit 10 comprises a central processing unit CPU 36, a RAM memory 38, a receiver 40 and an antenna 42 which communicate with each other via a data bus 44. The base 10 is powered by a battery (not shown) and is provided with a key-operated switch 46 for setting the base unit to a code learning mode. The "learn" switch 46 communicates with the CPU 36 via an input/output (I/O) interface 48. The base unit can also actuate a loudspeaker L and a visual warning lamp w in the I/O interface. The base unit 10 is additionally provided with an alphanumeric display 47 by means of which an observer can identify that a signal has been received from a particular base unit. In the present embodiment an LCD display is used which increases its reading by one each time a new code is stored. In addition to the code, each remote unit also transmits information identifying the type of sensor, and this information is stored in the RAM memory 38 in combination with the code. Thus, when no longer in the learning mode and a coded signal is received, the appropriate identity (e.g. "window sensor 01" etc) is displayed on the display 47 to enable an observer to identify the source of the signal. The display may also be able to identify the cause of the signal, e.g. actuation of a sensor or low battery in the sensor. This procedure is repeated with the remote unit 14 (and any other remote units) until the base unit 10 has received and stored a code and signal identifying the type of sensor from each of the remote units. The learn switch 46 is then de-activated, and thereafter receipt of any one of the code signals from the remote units can be identified as originating from a particular remote unit.

In order to set the codes for the remote sensors 12,14 the learn switch 46 of the base unit 10 is firstly actuated to put the base unit into a learn mode. A first unit 12 is then switched on which actuates the binary counter 32 which thus starts to count. The switch 34 is then closed which, in

combination with the software in the unit, causes the counter to stop. The number which exists in the counter is thus unpredictably generated and is then fed to the CPU and in turn is transmitted via the transmitter 26 and antenna 28, with additional

information such as the status of the sensor and the status of peripheral circuits such as battery

condition. The transmitted signal received by the base unit 10 in its learn mode which stores the code in its RAM 38 and thereafter in future use when not in the learn mode associates the signal as originating from the specific base unit 12 and actuates the loudspeaker L and the warning lamp W.

The generation of the identifying code is

illustrated in the flow chart of Fig. 2 and the control of the hardware is illustrated in the diagram of Fig. 3. In summary, the operation is as follows.

1. Switch Remote Receiver 10 to "Learn Mode" via switch 46.

2. Switch Transmitter unit 12,14 to "Generate Code Mode" by powering up unit initially to set counter running, e.g. by inserting a battery. 3. Momentarily actuate switch 34 to stop

counter. This signal is automatically transmitted to the remote receiver 10 in addition to information identifying the type of sensor and status information (e.g. battery condition).

4. Switch Receiver back to "Normal Mode". The remote unit transmitter automatically reverts to

"normal mode".

5. Units can now communicate.

6. The sequence may be repeated for other units, or the first unit re-programmed with a new code.

Alternatively, the remote units may be configured by software in the ROM 29 to run the counter 32 while the switch 34 is depressed or for a period between two depressions of the switch. In all cases the objective is to produce an unpredictable time period, in which to run the counter. Other scrambling and coding techniques may be used to act on the code as generated above in order to increase the level of security.

Another method is to transmit the real time and use this as a distinct identifier (either directly or in coded form.

The code learning cycle may be re-set and/or initiated by a power-down power-up cycle of the remote unit, followed by the operation of the system 32.

This operation assumes that the main unit has been made ready to accept the transmitted code by

actuation of switch 46.

The transmission uses a 16 bit code to convey the code and further bits as required to indicate status and parity signals. Using a 16 bit binary code ensures that there are 65,536 possible combinations for use by the immediate system and an other adjacent: system (which has sufficient power to generate a received signal in the main unit receiver).

At the receive node, in this example the main unit of the alarm, there is an associated learn switch 46. When the learn switch is set the receive unit is enabled to look for a received signal pattern which is transmitted from a remote transmitter mode (when the switch 32 is actuated). Upon receipt of a valid identifying code the receive node microprocessor would store the code in non-volatile memory, simultaneously recording the identifier code and other data such as the type of device. The process would be repeated for each sensor in turn, until all sensor/transmitter nodes are recorded.

The main unit (the receive node) is fitted with a battery reserve power-pack to enable it to function during power interruptions. However, in the event of a total loss of power the system retains the

previously stored codes in the non-volatile RAM. However, the system may be re-activated by use of the individual sensor teach/learn sequences preceded by a power down in the remote units. When completely re-activated the system codes are virtually guaranteed to be different numbers by virtue of the code numbers re-generated.

In another embodiment, shown in Fig. 4 the binary counter of at least one of the remote units is

replaced with an electronic real time clock 50, the hardware being otherwise identical. Thus, after power-up of the remote units 12',14', actuation of the switch 34 stops the clock 50. The CPU reads the time and causes the transmitter 26 to transmit the time as the coded signal, together with additional information such as the status of the sensor and the status of peripheral circuits such as battery condition, to the base unit 10 in the "learn" mode.

In another embodiment, shown in Fig. 5, the binary counter of at least one of the remote units is replaced with an electronic random number generator 52, the hardware being otherwise identical.

Thus, after power up of the remote units 12",14", actuation of the switch 34 stops the random number generator. The CPU reads the most recent number generated and causes the transmitter 26 to transmit the number as the coded signal, together with additional information such as the status of the sensor and the status of peripheral circuits such as battery condition, to the base unit 10 in the "learn" mode.

The generation of a code within the processor of a microchip or the hardwired logic code generator, associated with an operational function integral or separate to a communication channel, makes the concept a powerful identifier for other applications. These applications are specially useful for security devices working within radio communicating proximity to other, separately targeted security devices working on the same channel thereby being recognised as being

specific to one particular system. Further

applications include interference free remote control power sockets, which may be used by parents for example to prevent children's over use of computer games, or invalids to enhance difficult access.

This application is therefore to include the assignment of an identifying code, randomly (or pseudo-randomly) generated, to any system which uses the concept to discriminate specific nodes/devices via a teach/learn procedure.

The invention is not restricted to the details of the foregoing embodiments. For example, the

communication between the base unit and the remote units need not be by radio for example, communication can be achieved by means of a hard wired connection, an infra-red link or a microwave link.

Also, the base unit 10 may be arranged upon initial actuation to create a coded signal which is learned by a remote unit such as a siren or automatic telephone dialler which is able to receive and learn a signal in addition to the ability to transmit to the base unit.

Subsequent receipt of the coded signal by the remote unit allows it to be controlled.

Claims

1. An identifying system comprising a remote unit, a master unit and means for transmitting a signal from the remote unit to the master unit, the remote unit comprising means for unpredictably

2. A system as claimed in claim 1, wherein the remote unit comprises means for generating a coded signal.

3. A system as claimed in claim 2, wherein the coded signal is a binary coded signal.

4. A system as claimed in claim 2 or claim 3, wherein information is transmitted in addition to the code.

5. A system as claimed in any of the preceding claims, wherein the remote unit comprises means for switching it into a code-originating and transmitting mode and the master unit comprises means for switching it into a learning mode to store a newly-originated code.

6. A system as claimed in any of the preceding claims, wherein the remote unit comprises an electronic counter and means for stopping the counter at a number which becomes an originating code.

7. A system as claimed in claim 6, wherein the means for stopping the counter comprises a switch.

8. A system as claimed in claim 7, wherein subsequent to the transmission of the original

identifying signal, actuation of the switch results in transmission of a test signal.

9. A system as claimed in any of claims 6 to 8, further comprising means for commencing counting by the counter.

10. A system as claimed in claim 9, wherein the counter is started when the remote unit is actuated.

11. A system as claimed in any of the preceding claims, wherein the remote unit comprises a random or pseudo-random number code generator.

12. A system as claimed in any of the preceding claims, wherein the remote unit further comprises scrambling means for altering the generated code prior to transmission.

13. A system as claimed in any of the preceding claims, wherein the remote unit comprises a clock and means for stopping the clock, the time on the clock forming the identifying signal.

14. A system as claimed in any of the preceding claims, comprising a plurality of remote units.

15. A system as claimed in any of the preceding claims, comprising a plurality of master units.

16. A system as claimed in any of the preceding claims, wherein the remote unit and the master unit communicate in a wire-less manner.

17. A system as claimed in any of the preceding claims, further comprising means for replacing an existing identifying signal with a new identifying signal.

18. A system as claimed in any of the preceding claims, wherein the base unit can transmit a coded signal to a remote unit which is additionally capable of receiving the signal and subsequently recognise and use that signal.

19. An intruder detection system comprising a system as claimed in any of the preceding claims, comprising a plurality of remote units and wherein each remote unit comprises a detector which transmits a signal to the master unit upon actuation.