GB2237668A

GB2237668A - Security signalling system

Info

Publication number: GB2237668A
Application number: GB8922408A
Authority: GB
Inventors: Ian Alexander Owers
Original assignee: Racal Guardall Scotland Ltd
Current assignee: Carrier Fire and Security UK Ltd
Priority date: 1989-10-05
Filing date: 1989-10-05
Publication date: 1991-05-08
Anticipated expiration: 2009-10-05
Also published as: FR2653921A1; GB2237668B; GB8922408D0; FR2653921B1; DE4030993A1

Abstract

A security signalling system comprises a receiving station (e.g. RSI) at each of a number of different sites (e.g. banks) and a group of transmitters (e.g. T1-1, T1-2 ... T1-8) associated with each receiving station. The transmitters at each site transmit information containing a respective access code which is recognisable only by the associated receiving station. A group of mobile transmitters (P1, P2), e.g. carried by security guards in cash-in-transit vans, transmit information containing a common access code which can be recognised by any of the radio receivers, enabling an alarm to be raised immediately at any of the sites. <IMAGE>

Description

G 1 - SECURITY SIGNALLING SYSTEM This invention relates to security

signalling systems and particularly to such systems having mobile transmitters provided, for example, in security vehicles, such as cash-in-transit vans.

Some banks have self-contained security signalling systems comprising several radio transmitters which can be activated by personnel in an emergency in order to transmit an alarm signal to a local receiving station at the same bank. The transmissions from such radio transmitters contain a unique access code, recognisable only by the associated receiving station. By this means, the receiving station in each bank is prevented from responding to transmissions from other banks which might otherwise give rise to false alarms.

Such security signalling systems are unable to recognise radio transmissions from mobile transmitters provided in security vehicles, such as cash-in-transit vans. Thus, in the event of an emergency, such as an attack made on a vehicle in the vicinity of a bank, there could be a considerable delay before assistance can be rendered.

According to the present invention, there is provided a security signalling sys,----m comprising a plurality of 2 - 9 receivers, each located at a respective site, a respective group of transmitters associated with, and capable of transmitting information to, each receiver, the information transmitted by the transmitters in each group containing a respective access code recognisable only by the associated receiver, and at least one mobile transmitter for transmitting information containing a common access code recognisable by any of the receivers.

Preferably the mobile transmitters are associated with one or more security vehicles, such as cash-in-transit vans. A mobile transmitter may be a fixture inside the security vehicle or alternatively could be carried by a security guard travelling in te vehicle.

The receivers, the transmitters in each group and the mobile transmitters may operate at radio frequency.

1.4 Each receiver may have a first rec.ogni&R-JLon means for recognising the respective access code contained in the information transmitted by any of the transmitters associated with the receiver, and a second recognition means for r_ecognising the common access code contained in information transmitted by any of the mobile transmitters.

According to a further aspect of the invention, there is 1 (IF provided a receiver suitable for use in a security signalling system, comprising a receiving circuit for receiving a radio transmission, a first recognition means for recognising a first access code in a received radio transmission, a second recognition means for recognising a second access code in the received radio transmission, the first and second access codes being different, and means for generating a respective output signal in response to recognition of the first and second access codes by the first and second recognition means respectively.

A security signalling system in accordance with the invention is now described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a block diagram showing several security signalling installations; Figure 2 is a block circuit diagram showing a transmitter in the system; Figure 3 is a diagram showing blocks of digital data forming signals transmitted in the system; and Figure 4 is a block circuit diagram showing a receiving station in the system.

The security signalling system shown in Figure 1, comprises three security signalling installations 1, 2 and 3, each being located at a different site (in this case in a respective bank), and two mobile transmitters, each being associated with a respective security vehicle, for example a cash-in-transit van. Such transmitters would normally (though not necessarily) be carried by security guards travelling in the vehicle.

It will be understood that although this embodiment, given by way of example, has three security signalling installations and two mobile transmission units, the system may have a greater or smaller number of these components.

Each installation 1,2,3 comprises a respective group of local radio transmitters T1-1, T1-2.... T1-8 (for installation 1); T2-1, T2-2... T2-8 (for installation 2) and T3-1, T3-2.... T3-8 (for installation 3), and also a respective radio receiving station RS1, RS2 and RS3.

The transmitters in each group may be activated manually in order to transmit an alarm signal to the associated receiver in the event of an emergency. To that end, the W (P transmitters may be carried by personnel or, alternatively, located at strategic positions in the bank, at cashier's desks for example. Alternatively, or in addition, the transmitters in each group may be activated in response to a detection signal generated by a security sensor used, for example, to detect unauthorised entry into a secure area. Such sensors may take the form of infra-red detectors, or intrusion sensors having pressure sensitive contact pads placed strategically, near a window or door, for example.

Figure 2 shows, by way of example only, a suitable radio transmitter (e.g. T1-1) which can be activated manually by closing a switch 5. The transmitter has an input circuit 6 which is connected across the switch by a pair of lines 7,8. When switch 5 is closed, the input circuit 6 generates an appropriate response signal (indicating that an alarm has been raised) which is then encoded by an encoding apd timing circuit 9 and passed to a radio transmitter 10 for onward transmission, by radio, to the associated receiving station (RS1 in this case), via a transmitting antenna 11. The transmitter would usually have a compact and unobtrusive design, and would have a battery power supply 12. The power supply connections are not shown in the drawings.

a Signals transmitted by the transmitters are in digital form, and Figure 3 shows one format which the transmitted digital signals could take.

Referring to Figure 3, each transmitted signal comprises a first data block B1 (eight bits long), termed an access code, which identifies unambiguously the respective installation to which the transmitter belongs. Accordingly, each installation is ascribed its own, unique access code. The next part of the transmitted signal comprises a second data block B2 in the form of a zone code (comprising four bits) which identifies the zone (e.g. a room) in the bank within which the transmitter is located. Data block B3 (also comprising four bits) is a transmitter code which distinguishes the transmitter, responsible for the transmission, from all the other transmitters in the same installation.

The final data block B4 (again four bits) represents information; in this case the state (i.e. "open" or "closed") of switch 5.

As has been described already, the transmitters in each installation are all arranged to transmit the same respective access code whIch, in effect, identifies the installation unambiguously and distinguishes it from all (p the other installations. Likewise, the receiving station in each installation is arranged to respond only to the correct access code (produced only by the transmitters in that installation) and does not respond to transmissions (from other installations) containing different access codes. In this way, each installation.is self-contained, and interference between the different installations is prevented.

Figure 4 shows a receiving station (e.g. RS1), in block schematic form. This has a receiving antenna 20 connected to receiving circuitry 22 for receiving and appropriately processing digital signals from any of the transmitters (including those in other installations) which are within range. The received signals are routed to a de-modulating circuit 24 which de-modulates signals having the correct modulation format, extraneous signals, having an incorrect modulation format, being rejected. The de-modulated signals are then passed to a fir-st recognition circuit 26 which compares the access code contained in the received signals (in data block B1) with a pre-programmed access code (i.e. the correct access code for that installation) stored in its memory. If the recognition circuit recognises the access code the received signals are passed to a data extraction circuit 28 which extracts the data block B4 and initiates an 8 appropriate response. For example, if data block B4 indicates that switch 5 is closed (the alarm condition), the data extraction circuit generates an audible, or alternative form of warning, or transmits an alarm signal to a central signal monitoring station.

The mobile transmitters Pl, P2, shown in Figure 1, could be programmed to transmit the access code for a selected one of the sites (Site 1, say), which would be recognised by the respective receiving station (RS1). However, this arrangement would be impractical if, as is normally the case, the security vehicles, with which transmitters Pl, P2 are associated, are required to move from site-to-site, since the accss code would need to be changed to that appropriate for each new site visited.

With a view to alleviating this problem, the mobile transmitters are preprogrammed to transmit a common access code which differs from the access codes to which the first recognition circuits 26 (in receiving stations RS1, RS2 and R53) are programmed to respond.

Such receiv-ing stations now contain a second recognition unit 30 which is also connected to the output of demodulation circuit 24, b"t is preprogrammed to respond only to the common access code contained in the trans- 9 - missions of the mobile transmitters Pl, P2. As before, if the second recognition circuit 30 recognises the common access code, the received signals are passed to a further data extraction circuit 32 which initiates an appropriate response. The first and second recognition units 26,30, and their respective data extraction circuits 28,32, could be combined in a common circuit, producing a common output signal containing an appropriate data flag indicating whether or not the common access code has been recognised.

(p The described system ensures that a transmission from any mobile transmitter will be recognised by each, and every receiving station within range including, most importantly, the nearest of them. In this way, therefore, a security guard making a delivery at a bank has the ability to summon immediate assistance, regardless of its location.

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Claims

1. A secui-,ity signalling system comprising a plurality of receivers,, each located at a respective site, a respective grroup of transmitters associated with, and capable of transmitting information to, each receiver, the information transmitted by the transmitters in each group contalming a respective access code recognisable only by the associated receiver, and at least one mobile transmitter for transmitting information containing a common access code recognisable by any of the receivers.

2. A security signalling system as claimed in claim 1, wherein the rweivers, the transmitters in each group and the or each, nnobile transmitter operate at radio frequency.

3. A se=rity signalling system as claimed in claim 1 or claim 2, wherein each receiver includes first Ition!means for recognising the respective access recognI code contai in the information transmitted by any of the transmitters associated with the receiver, and second recognition mnz for recognising the common access code contained Ls information transmitted by any of the mobile transmitters- 1 (p 1

4. A security signalling system as claimed in claim 3. wherein the first and second recognition means comprise respective parts of the same recognition circuit.

5. A security signalling system as claimed in claim 4, wherein the recognition circuit is capable of generating a single output signal containing information which distinguishes recognition signals produced by the first and second recognition means.

6. A security signallin system as claimed in any one of claims 1 to 5, wherein the mobile transmitters are associated with one or more security vehicles, such as. cash-in-transit vehicles.

7. A radio receiver suitable for use in a security signalling system, comprising a receiving circuit for receiving a radio transmission, a first recognition means for recognising a first access code in a received radio transmission, a second recognition means for recognising a second access code in the received radio transmission. the first and second access codes being different, and means for generating a respective output signal in response to recognition of the first and second access codes by the first and second recognition means respectively.

1

8. A security signalling system substantially as hereinbefor.e described with reference to the accompanying drawings.

dr

9. A radio receiver for use in a security signalling system substantially as hereinbefore described with reference to Figure 4 of the accompanying drawings.

(0351H) Published 1991 atThe RatentOffice.St2te House. 66/71 High Holhorn. LondonWCIR47P. Further copies may be obt2ined frorn Saks Branch. Unit 6. Nine Mile Pbint. Cwmfc"ch. Cross Keys, Newport. NPI 7HZ. Printed by Multiplex techniques lid. St Mary CTay. KenL