GB2300739A

GB2300739A - Remote control apparatus

Info

Publication number: GB2300739A
Application number: GB9509614A
Authority: GB
Inventors: Nick Sims
Original assignee: GARDINER TECHNOLOGY
Current assignee: GARDINER TECHNOLOGY
Priority date: 1995-05-12
Filing date: 1995-05-12
Publication date: 1996-11-13
Anticipated expiration: 2015-05-12
Also published as: GB2300739B; GB9509614D0

Abstract

A remote control apparatus (e.g. for controlling an alarm system) comprises a transmitter (14) operable by the user to generate a signal encoded with data and a receiver (12) operative to receive the signal and decode the data from it. The data comprises an identifying code which identifies the transmitter (14) from which it originated and a sequence code. The sequence code varies between successive operations of the transmitter and comprises a number generated algorithmically by an operation performed upon a seed value. The receiver (12) verifies the authenticity of a received signal by determining whether the received sequence code is one expected from the transmitter identified by the identifying code.

Description

REMOTE CONTROL APPARATUS The present invention relates to remote control apparatus, and in particular to remote control apparatus which is resistant to unauthorised actuation, for example for controlling a security alarm system.

Various remote control systems are known for alarms and other devices. For example, television sets and video recorders are often provided with remote control devices capable of transmitting a multiplicity of distinct signals carried on a modulated infra-red beam.

In this case, security is not an issue. Indeed, remote control apparatus intended for one model of equipment will generally operate with all examples of that model.

Many cars are equipped with a remote control for a security alarm and/or door locking, signals being transmitted between a hand-held transmitter and a vehicle-mounted receiver on a radio or an infra-red carrier. Proprietary circuits can be used to encode the transmitted signal with a code to which the receiver uniquely responds, the code being selectable from many hundreds of millions. Thus a receiver will react only to a signal from an authorised transmitter. A disadvantage of such systems is that it is readily possible to intercept and record the signal emitted from the transmitter, for subsequent regeneration. This limits the security of such systems and has contributed to their relatively poor acceptance in the control of alarms for buildings. Additionally, it is necessary to preset receivers and transmitters for use as matched pairs.This is inconvenient for the user if a new or replacement transmitter must be obtained, and inconvenient for manufacturers who are faced with difficulties in administration.

It is an aim of the present invention to provide remote control apparatus capable of permitting remote control of equipment such as an alarm system with a high degree of security. It is also an aim of the invention to avoid the need to match preset receivers and transmitters in a remote control apparatus. In addition, it is an aim of the invention to allow users readily to add and delete transmitters authorised for use with the system.

In a first of its aspects the invention provides remote control apparatus comprising a transmitter operable by the user to generate a signal encoded with data and a receiver operative to receive the signal and decode the data from it, in which the data comprises an identifying code which identifies the transmitter from which it originated and a sequence code, the sequence code varying between successive operations of the transmitter and being a number generated algorithmically by an operation performed upon a seed value, the receiver operative upon receipt of a signal to verify its authenticity by determining whether the received sequence code is one expected from the transmitter identified by the identifying code, and to perform an appropriate action.

Provided that the number of available sequence codes is high, and the algorithm by which successive sequence codes is not apparent, it is very difficult to generate an acceptable signal other that by means of a genuine transmitter.

The seed value may conveniently be the sequence code of the data of the previous operation of the transmitter.

Typically, the data will be encoded as a multi-bit binary number on a modulated radio or infra-red carrier. However, the principle of the present invention can be extended to any suitable carrier, modulation scheme or any other means by which a data signal may be transmitted.

In one preferred embodiment, the data comprises a 32 bit sequence code and a 16 bit identifying code. This permits 232 (over 4294 million) unique sequence codes to be generated by 65536 uniquely identified transmitters.

Preferably, on receipt of a signal, the receiver verifies as authentic a signal whose data corresponds to that which would be contained in one of a predetermined number of subsequent signals subsequent to the last received from an identified transmitter. In this way, the receiver can re-synchronise itself with a transmitter that has been activated (with corresponding advancement of its sequence code) to generate a signal not received by the receiver.

The action generated by the receiver on receipt of a signal is typically used to control the function of an apparatus under remote control. Such apparatus may be an alarm system.

The remote control apparatus may conveniently be operative to generate signals equivalent to those generated by local controls of a controlled apparatus (eg. a conventional alarm panel). In this manner, existing apparatus may be retro-fitted with remote control apparatus.

For example, the system may generate signals equivalent to those generated by a conventional remote input keypad for an alarm panel. Thus, an operation of the remote control system, the alarm panel receives signals substantially indistinguishable from those received in its conventional mode of operation. A further advantage of this arrangement is that the system can easily be made retro-fittable to a range of panels.

In a second aspect, the invention provides a security alarm system comprising remote control apparatus according to the first aspect of the invention.

In a third of its aspects the invention provides a method of operation of a remote control apparatus comprising a receiver and one or more transmitters, comprising: operation of a transmitter to generate a signal comprising data including a predetermined identifying code, invariant between operations of the transmitter and a sequence code that varies algorithmically between operations of the transmitter; the receiving apparatus, on receipt of a signal, verifying that it is that of an authorised transmitter and, if this is confirmed, checking that the sequence code is one that would be expected from that transmitter and then performing an action appropriate to the outcome of these tests.

An embodiment of the invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 represents diagrammatically an alarm system incorporating a remote control apparatus embodying the invention; Figure 2 represents data in a signal emitted by a transmitter of the system of Figure 1; Figure 3 is a simplified block diagram of a receiver of the system of Figure 1; and Figure 4 is a simplified block diagram of a transmitter of the system of Figure 1.

An alarm system illustrated in Figure 1 comprises a control panel 10 and remote control apparatus embodying the invention comprising a receiver 12 and one or more transmitters 14.

The control panel 10 is of conventional configuration and has a keypad 16 by means of which a user can control its operation and a status display 18.

Additionally, it has a first interface 17 intended for connection to a remote keypad 19 in a conventional manner, through a multiple electrical conductor 21, the remote keypad 19 then emulating the function of the keypad 16.

As shown in Figure 3, the receiver 12 comprises an aerial 22 for receiving radio signals. The output of the aerial is fed to a decoding module 24 which converts suitable received radio signals to a stream of electrical binary data. A processing module 26 receives such data from the decoding module 24. The processing module 26 is connected for output to an interface module 28 operative to convert data that it receives from the processing module into signals that emulate key press actions on a remote keypad. Output from the interface module 28 is connected to a second interface 29 of the control panel 10 though a multiple electrical conductor cable 20. The processing module 28 is connected to a non-volatile random access memory module (NVRAM) 30 in which it can store data for future retrieval.

The transmitter 14, as shown in Figure 4, comprises a processor module 40, which receives input from a pushbutton actuating switch 42, and which is connected to a non-volatile random access memory module (NVRAM) 41 in which it can store data for future retrieval. The processor module 40 is operative to generate repeatedly an output of a stream of binary digits encoded in an electrical signal. This is fed to an encoding module 44 which converts them to a form suitable for transmission as a radio signal. Transmission is achieved through an aerial 46.

On operation of the switch 42, the transmitter thus generates a signal for transmission. The signal comprises binary data encoded in a radio signal, the form of the binary data being illustrated in Figure 2.

To generate the binary data, the processor module 40 first calculates a sequence code and stores it in an internal buffer. The sequence code is a 32-bit binary number and is calculated by applying a sequence algorithm to the sequence code used in the previously transmitted data, which is stored in the NVRAM 41.

The important characteristics of the sequence algorithm are as follows: 1. It must be kept secret by the manufacturer of the system.

2. Its nature should not be readily apparent from the output that it generates.

3. It should generate in successive applications all or a high proportion of all of the possible values that the sequence number can adopt, by successive application to its last output value.

There are many pseudo-random number generators published in computing texts that fulfil all of these requirements.

The binary data further comprises an identifying code which is fixed for any one transmitter. This is a 16bit binary value and is also stored in the buffer ready for output.

It will be appreciated that the same 150 bit signal is sent repeatedly while the switch 42 is pressed. Once the switch 42 is released, the sequence code is updated so that subsequently generated signals have a different sequence code.

A 16-bit data value may also be included in the data.

This may have a fixed value or may optionally be variable, as will be described below.

Additionally, extra bits may be added to the data for convenience of handling and error checking.

Once the data has been assembled, it can be transmitted. The processor module sends the data to the encoding module 44. This generates a signal which is radiated by the aerial 46.

The receiver 12 operates in two modes: a programming mode and a normal mode.

The receiver 12 enters programming mode on receipt of a programming control signal from the alarm panel 10.

In its programming mode, one or more transmitters 14 may be identified by a user as being authorised. On receipt of a signal from a transmitter 14, the receiver 12 checks to ensure that the transmitter (as identified by the identifying code in the signals data) has not already been authorised by looking for its identifying code in the NVRAM 30. For authorisation, the receiver 12 stores in its NVRAM 30 the identifying code of a transmitter 14, together with the received sequence code.

The receiver 12 then applies a translation algorithm to the identifying code combined with the sequence code to generate an actuating code of a format acceptable to the alarm panel 10. For example, it may comprise a sequence of four decimal numbers. This is then stored in the NVRAM 30, in association with the identifying code, and is also output to the alarm panel 10.

In normal mode, the receiver 12 first looks for the identifying code of a received signal in its NVRAM 30.

If the code cannot be found, then the received signal has been emitted from an unauthorised transmitter, and is rejected. If the identifying code is found, the receiver then applies the sequence algorithm to the corresponding sequence code stored in the NVRAM 30.

The resulting sequence code is then compared to that in the received data. If a match is found then the signal is regarded as being from an authorised transmitter.

Otherwise, the sequence algorithm is applied to the said resulting sequence code and the comparison procedure with the received data is repeated. This process will be repeated a predetermined number of times before the data is rejected as originating from a non-authorised transmitter.

Once a signal is identified as being from an authorised transmitter, the sequence code in the data contained in the signal replaces that code stored in the NVRAM 30.

The actuating code is then output to the alarm panel 10.

This matching process ensures that a transmitter will be correctly recognised even if it is activated a number of times without its signal being received by the receiver. It will also be seen that through the programming process, any compatible transmitter can be authorised for use with the receiver, without the need to match one to the other.

The receiver 12 is connected to the alarm control panel 10 to emulate signals received from a remote keypad. A typical alarm system is controlled through entry of a code number at a keypad of, say, four digits. The operation of the alarm system is determined by the particular code entered on the keypad. In the present embodiment, a code for controlling the alarm system is generated by application of a translation algorithm to the identification code and the sequence code. In this way, different transmitters can be assigned to perform different actions in control of the alarm system. More than one receiver can be arranged to control the alarm system. They can generate the same user code provided that they use the same translation algorithm, and provided that they are all programmed by a single operation of the transmitter, or they could generate different user codes from one transmitter.

Alternatively, in an alternative embodiment, the code number may be generated by translation of the identifying code only. In this way, multiple receivers can be programmed to recognise the same transmitter in multiple transmission, since the code generated will not vary between transmission.

Preferably, the or each receiver 12 is operative to detect that the alarm control panel 10 has entered programming mode, whereupon it also enters programming mode.

It will be appreciated that the control panel will be actuated only when a signal is received by the receiver 12 from a recognised transmitter 14, and when the receiver, in response to that signal, generates a code acceptable to the alarm panel 10. Thus, authorisation of a particular transmitter can be revoked by cancellation of its code at the alarm panel 10 only, a procedure familiar to an alarm system controller.

As an example, assume that the identifying code of a transmitter 14 allocated to user No. 2 of an alarm system is 5555h and the next sequence number to be transmitted is CCCCCCCCh.

At the alarm panel 10, the user enters a master code and selects an option to program a user code for, say, user 2. The transmitter 14 destined for user 2 is then activated to send a signal to the receiver 12, which receives the values given above. The receiver 12 applies the translation algorithm to the received identifying value 5555h and the sequence code CCCCCCCCh to generate a 4-digit code, say, 9901. This code is then fed through the cable 20 to the alarm panel 10 which behaves as if the code 9901 were directly entered at a keypad. Any further programming information required is then entered by the user at the control panel 10.

Following this, whenever user 2 activates his or her transmitter 14 in range of the receiver 12, the code 9901 is received by the control panel 10 as if it had been entered at a keypad.

It will be seen that undesirable user codes could occasionally be generated. For example, the identifying code of a particular transmitter 14 may translate to a code such as 5678, which could pose a security risk, or might be a duplicate of an existing code. Accordingly, the receiver 12 preferably is operable to check the generated code on programing and generate algorithmically a second (or subsequent) code if required. This can be conveniently achieved by addition of the sequence code to the identifying code before application of the translation algorithm. If necessary, the transmitter can be operated repeatedly until a satisfactory combination of identifying and sequence codes are obtained.

The data value of the transmitted signal can be used to influence the code generated by the receiver on receipt of a signal. At its simplest, one or more additional switches could be provided on the transmitter to instigate different control functions by changing the data value. For example, one value of data may indicate that a part-set is required and another might indicate that a "duress" condition exists and out the alarm panel in a mode in which it appears to be unset, but is, in fact, issuing a silent alarm. The data signal may be varied by, for example, the user pressing the switch 42 a number of times in quick succession.

An alternative manner of controlling these functions is for the receiver 14 to detect multiple actuations of a transmitter within a predetermined time window, and to vary the generated code accordingly. For example, on receipt of a valid signal, the receiver could generate a setting code, but if a second signal is received within, say, 3 seconds, setting would be cancelled, and a part-set sequence enabled clearly. This principle could be extended to control other functions of the alarm system.

In another mode, the receiver 12 may be configured to generate just one code on receipt of a signal from any authorised transmitter. (Otherwise, programming would take place as described above.) In this way, the panel may be controlled by many more users than the panel itself is capable of recognising. However, the users effectively operate the system "anonymously" so security may be less than in the preferred mode of operation described above.

Claims

1. Remote control apparatus comprising a transmitter

operable by the user to generate a signal encoded with data and a receiver operative to receive the signal and decode the data from it, in which the data comprises an identifying code which identifies the transmitter from which it originated and a sequence code, the sequence code varying between successive operations of the transmitter and being a number generated algorithmically by an operation performed upon a seed value, the receiver operative upon receipt of a signal to verify its authenticity by determining whether the received sequence code is one expected from the transmitter identified by the identifying code, and to perform an appropriate action.

2. Remote control apparatus according to claim 1 in which the seed value is the sequence code of the data of the previous operation of the transmitter.

3. Remote control apparatus according to claim 1 or claim 2 in which the data is encoded as a multi-bit binary number on a modulated radio or infra-red carrier.

4. Remote control apparatus according to any preceding claim in which the data comprises a 32-bit sequence code and a 16-bit identifying code.

5. Remote control apparatus according to any preceding claim the receiver being operative, on receipt of a signal, to verify as authentic a signal whose data corresponds to that which would be contained in one of a predetermined number of signals subsequent to the last received from an identified transmitter.

6. Remote control apparatus substantially as described herein with reference to the accompanying drawings.

7. In combination, remote control apparatus according to any preceding claim and apparatus under remote control in which the action generated by the receiver on receipt of a signal is used to control the function of an apparatus under remote control.

8. A combination according to claim 7 in which the apparatus under remote control is an alarm system.

9. A combination according to claim 7 or claim 8 in which the remote control apparatus is operative to generate signals equivalent to those generated by local controls of a controlled apparatus.

10. A combination according to claim 9 in which the remote control apparatus is operative to generate signals equivalent to those generated by a conventional remote input keypad for an alarm panel, such that on operation of the remote control apparatus, the alarm panel receives signals substantially indistinguishable from those received in its conventional mode of operation.

11. A security alarm system comprising remote control apparatus according to any one of claims 1 to 6 invention.

12. A method of operation of a remote control apparatus comprising a receiver and one or more transmitters, comprising: operation of a transmitter to generate a signal comprising data including a predetermined identifying code, invariant between operations of the transmitter and a sequence code that varies algorithmically between operations of the transmitter; the receiving apparatus, on receipt of a signal, verifying that it is that of an authorised transmitter and, if this is confirmed, checking that the sequence code is one that would be expected from that transmitter and then performing an action appropriate to the outcome of these tests.

13. A method of operation of a remote control apparatus comprising a receiver and one or more transmitters substantially as described herein with reference to the accompanying drawings.