WO1995000936A1

WO1995000936A1 - Identification beacon

Info

Publication number: WO1995000936A1
Application number: PCT/GB1994/001360
Authority: WO
Inventors: Klaus Norbert Tusch; Philip Wilmott
Original assignee: Colebrand Limited
Priority date: 1993-06-23
Filing date: 1994-06-23
Publication date: 1995-01-05
Also published as: AU6978794A

Abstract

An identification beacon (B) is suitable to send out an identification signal (I) in response to a call-up signal (X), but preferably only if the call-up signal is from an approved source (C) and only when it is safe for the operator of the beacon for the identification signal to be transmitted. The beacon is thus provided with a receiver (R) and a transmitter (T). The receiver responds to a call-up signal of suitable parameters to cause the transmitter to send an interrogation signal (Y) to the caller. If the receiver then receives from the caller a satisfactory response (Z) to its interrogation signal, it causes the transmitter to transmit an identification signal (I). An optional override switch (O) is provided for the operator to prevent transmission of the identification signal in certain circumstances and a paging device (P) may be provided to alert the operator that the beacon is ready to transmit an identification signal in response to a call-up signal but is presently inhibited by him from doing so. The received signals may include control signals to change the nature of the signals to be transmitted or the criteria for acceptability of received signals; alternatively, these changes may be made automatically in response to a given number including one of signal interchanges with a controller.

Description

IDENTIFICATION BEACON

A controller may wish to be able to locate and control his operators without danger of interference from or giving information to unauthorised persons.

The invention provides an identification beacon as set out in claim 1. Among the components are receiving means and transmitting means. When the receiving means receives a signal from the controller, the transmitting means is arranged to send back an interrogation signal to check that the security has not been breached. When the receiving means receives a satisfactory reply, the transmitting means is arranged to transmit the identification signal. The received signals may include a control signal to control the identification signal transmitted.

The identification signal may be a coded signal, whose code is unique to that operator. The controller can use a homing device to locate the source of that coded signal or the identification signal may be a location signal whose content gives the location of the operator; the operator may use the Global Positioning System in which reference to satellites enables his position on the ground to be given with great accuracy.

If security has been breached, a non-authorised person may call up the operator; without the interrogation signal transmission and the operator's response only to a satisfactory reply, the operator might be tricked into revealing his identity or location to the wrong person.

The beacon may be provided with means to control the transmission of the identification signal, so that in spite of a satisfactory reply to the interrogation signal, it is inhibited from transmitting an identification signal. This might be necessary if the operator has encountered a dangerous situation. With the control means operated, the beacon may simply act as a pager to indicate to the operator that he has been "called" - the indication being that of a pager - a visible, audible or other sensory signal, such as vibration. The operator can then cause transmission of the identification signal when the dangerous situation is over.

The control signal may control the nature of the interrogation signal and of the criteria for a satisfactory reply to be used at the next interchange of signals or after a certain number of such interchanges. Alternatively, any one or more of the receiving channel of the beacon, the interrogation signal and the criteria for satisfactory response may be changed automatically after a predetermined number (which may be one) of signal interchanges with the controller. For this purpose, the beacon may have a sequence of modes; after a first interchange of signals with a satisfactory reply being received at the receiver, the receiving means and transmitting means may be changed to a second mode in which the receiving means only responds to a control signal of a different format and/or changes the parameters of a reply which is satisfactory and/or in which the interrogation signal is changed. Thus if a hacker manages to work out the parameters of one interchange between the controller and the operator, he will not then be able to deceive the beacon by sending his own signals within those parameters because the beacon will have followed its sequence of modes and changed at least some of the parameters. The sequence must of course be known to both the controller and the operator but this is easily arranged by suitable programming of software.

The control and interrogation signals are most suitably at radio frequencies, for example in the UHF band around 400 MHz. Broadcast transmission, as distinct from use of highly directional lasers, is convenient when the relative location of the recipient is not known at the time of transmission. However, directional systems such as microwave links are preferred when relative locations are known. Satellite communications are suitable, particularly for the transmissions from the beacon. The identifying signal can be in the infrared region so that it is only detected by infrared sensitive devices, and it could be coded for greater security.

The parameters of the identification signal which may be changed by control signals include its amplitude. As the distance between the beacon and the controller increases, it is desirable to increase the amplitude of the identification signal for satisfactory reception by the controller. Another parameter which can be changed is the signal content, the change becoming necessary when two beacons with identification signals of similar content approach each other and might be confused. Although the use of control signals to effect this change at the instance of the controller is one possible method, it is possible for the beacon to be provided with a sensor for sensing identification signals transmitted by other beacons in the vicinity. If an identification signal with the same or a similar code is sensed, the beacon can respond to such sensing by either inhibiting its own transmission of identification signals, or transmitting its own identification signal a predetermined time delay after receiving the similar signal. Suitable identification signals may include digital codes, and the similarity of the signals can be judged when predetermined digits of the codes are the same.

An example of the invention will now be described with reference to the accompanying drawing which is a diagrammatic block diagram of a beacon in relation to a controller. In the drawing, a controller C and a beacon B interchange signals X, Y and Z. The beacon has a receiver R to receive signals X and Z and a transmitter to send signal Y and an identification signal I. When the controller wishes to call up the beacon, he sends a signal X in a prearranged channel and of a prearranged format. He would use an aerial with a wide field of transmission if the location of the beacon is unknown to him at the time of transmission. The receiver R of the beacon receives the signal X and assuming it is of an acceptable format, determined by reference to criteria of acceptability in the beacon, the beacon transmitter T sends back to the controller an interrogation signal Y. On receipt of the interrogation signal, the controller sends back to the beacon a prearranged response to the interrogation signal Y, in the form of a security clearance signal Z. Provided that the signal Z received by the beacon receiver meets prearranged criteria, the beacon then operates. The operation of the beacon may be to transmit an identification signal I for a predetermined period from which the controller can take a fix in order to determine the position of the beacon accurately. A more sophisticated beacon may be in radio communication with satellites to obtain from them an accurate fix of its own position on the ground and the coordinates of that position can be transmitted in the identification signal back to the controller. This arrangement enables the transmission back to the controller to be of a shorter period and thus less susceptible to interference from or discovery by third parties.

One of the signals X and Z may contain a control signal which, after the receipt of the satisfactory signal Z, will cause the beacon to perform other duties. These duties include changing the nature of the identification signal to be transmitted, changing the channel or format of the signals from the controller to which it is responsive, and in particular changing a security code within one of the signals X and Z so that for each interchange of signals or after a predetermined number of interchanges of signals the code advances along a predetermined sequence, known to both the controller and the beacon and stored in their software. The control signals may also control the nature of the interrogation signal Y. The changes caused by the control signals are partly to change the nature of the identification signal to be transmitted by the beacon for operational convenience, and partly to change the security checking system between the controller and the beacon, to avoid interference by unauthorised third parties.

A situation may occur when the operator of the beacon does not wish the identification signal to be transmitted when it is called up by the controller. The beacon is for this purpose provided with an override switch 0 which diverts the signal which would normally cause transmission of the identification signal to a paging device P, which would simply notify in a private manner to the operator of the beacon that the controller wishes to receive an identification signal. This paging device may indicate to the operator by means of light, sound or vibration, for example. When the operator believes it is safe and convenient to send the identification signal, he can then change over the override switch 0 to cause the beacon to send the signal I.

The beacon has a sensor S which detects identification signals from other such beacons. The sensor compares the received signals with the identification signal it is presently programmed to transmit. If it is sufficiently similar, the transmitter T is caused to transmit an identification signal in timed relation to the received identification signal from other beacons. Alternatively transmission of its own identification signals can be inhibited.

Claims

1. Identification beacon comprising receiving means and transmitting means, the transmitting means being arranged to send an interrogation signal on receipt of a suitable first incoming signal by the receiving means and arranged to send a signal identifying the device and/or its location on receipt of a second suitable incoming signal at the receiving means after the transmission of the interrogation signal.

2. A beacon as claimed in claim 1 wherein the transmitting means is responsive to control signals received at the receiving means to change the nature of the signal it is arranged to transmit.

3. A beacon as claimed in claim 1 or claim 2 comprising means responsive to a given number of first suitable incoming signals to change the criteria for selecting suitable first and/or second incoming signals and/or to change the interrogation signal.

4. A beacon as claimed in any one of claims 1 to 3 comprising means for inhibiting transmission of the interrogation signal by the transmitting means.

5. A beacon as claimed in claim 4 comprising means for indicating to an operator of the device that a second suitable incoming signal has been received.

6. A beacon as claimed in any one of the preceding claims comprising means responsive to the reception of interrogation signals from other such beacons to control the transmission of said interrogation signal.