GB2207532A - Improvements in or relating to security systems - Google Patents

Abstract

A plurality of premises P1-P4 are interconnected so that each premise is able to monitor the security position of each other premise to detect if the alarm has been set, the alarm condition and if any interconnecting links have been tampered with. Signals are preferably transmitted at all times between the premises, the signals being of three types respectively to indicate a quiescent condition, a live condition and a security alarm condition. In the quiescent condition a signal comprising a burst of frequency is transmitted every X seconds, while in the live condition the burst is transmitted every Y seconds, where Y is substantially less than X. In the alarm condition, a signal comprising a continuous frequency is transmitted. <IMAGE>

Description

IMPROXE.IEN'TS IN OR RELATING TO SECt;RITY STSTES The present invention relates to security systems and more particularly to security systems for a number of properties geographically located close together.

A problem with present security systems is that they are normally individual to a property and when a security breach is detected result in an external bell being actuated or a telephone call to a police station often many miles away. With respect to the bell, firstly it is not a certainty that this will be heard and, with the high incidence of false alarms it is more possible that it will be ifrnorsd, at least for a considerable period.

With rospeet to ,Ie silent alarm actuated at the nearest police stat,is)n firstly even with fast response it may be many minutes before a local patrol can be alerted and arrive at the scene and secondly if the nearest patrol is already busy on a more urgent call the response time can be several hours. Since most burglaries are committed in a few minutes the present alarm systems are therefore proving unsatisfactory.

It is an object of the present invention to provide an alarm system which overcomes the above disadvantages.

The alarm system according to the present invention is an extension of the "Neighbourhood Watch" schemes where neighbours of goodwill bond together against a common threat.

The present invention therefore provides a security alarm system comprising an electronic control including transmission and receiving sections the transmission section serving to transmit an alarm condition to neighbouring premises to alert the occupants thereof and the receiving section serving to receive alarm conditions from one or more neighbouring premises to indicate an alarm condition within such premises.

Preferably the control circuitry includes means for identifying and indicating which of a plurality of premises is transmitting an alarm or other condition.

Preferably the electronic controls in the premises are connected by a simple 2 wire link. The electronic control circuitry includes means for detecting any disconnection of the link.

The system is preferably provided with a back up battery system such that disconnection of the mains power does not disable the system.

Embodiments of the present invention will now be described, by way of example with reference to the accompanying drawings in which: Figure 1 shows schematically a security alarm system according to the present invention; and Figure 2 shows block diagrammatically the electronic control circuitry for an electronic control box in one of the alarmed premises.

With reference to Figure 1 properties P1, P2, P3 and P4 are connected via links L1, L2, L3 and L-l. Link L may be omitted. More properties may be included in any link but preferably the number is between two to six to avoid too great a geographical distance between any of the properties. Each property is equipped -with a burglar alarm system of any known suitable type (e.g. infrared, pressure mat, door/window switches) and has a control box 10 to which links L1 to L4 are connected.

Regardless of how many premises are in the link the deterent effect of the system lies in the fact that a would be burglar cannot readily detect how man premises are in the link because the wires may not necessarily be on view. They can be passed for example through the sewage system or by burying in the ground. Since no high voltages or currents are involved there will be no need for any special protective precautions.

The control boxes 10 sere to monitor the alarm condition of their associated premises and to transmit any alarm condition to all of the other control boxes in the link ad also to detect and display any alarm condition from any other control box in the link. The display preferably includes an indication of which of the other connected premises the alarm condition originates from and may comprise an illuminated display and an alarm bell. This alarm bell may be used instead of an external alarm in the violated premises thereby providing a silent alarm system enabling the intruder to be observed and the police to be informed by a telephone call from one of the other premises in the link.

A prospective intruder must therefore consider that it is likely that within seconds of entry into a premise connected to this system he will be observed even if not actually apprehended. This is true even if he cuts the wire link since this will also signal an alarm condition.

One embodiment of circuitry effecting this alarm signaling is shown in Figure 2 to which reference is now made. Each control box 10 comprises basically three sections, a receive section, a transmit section and a monitoring section plus a plurality of indicators.

The transmit section comprises a number of security inputs 12, 14 and 16, 18 which in known manner provide an input to a latch 20 which provides an output via OR gate 22, to gate a signal oscillator 24 via gate 26.

The output of gate 26 is fed via a capacitor isolator to links L1 and L (for example).

The system may be set to a live or quiescent state by a switch 28. This provides via OR gate 22 and gate 26 respectively either a three second pulse burst every 24 seconds or every 48 seconds from a divider and timer circuit 30 to be detected and used as described hereinafter. The divider and timer circuit 30 is driven by a master oscillator 32 operating at 16, 384 Hz, in a preferred example, the output of oscillator 32 also being used as a clock input to a divide b N circuit 31 on the receive section.

In the receive section decoding of an input signal is controlled by a sequencer 36 which is clocked by a 4 Hz clock divided out by circuit 30.

Input signals from links L1 etc. are deisoiated by a capacitor and fed to a miser .10 in which, on a time division basis, a search is carried out in sequence for one or more the the sis channel fr.equencies as given in Table 1.

VIABLE ' Signal Frequencies CHANNEL Fs(z) 1 298 2 385 3 560 4 720 5 999 6 1340 It is noted here that six channels are specified. In a standard unit however four channels is a good compromise for connection of four premises. If less are connected then one or more channels can be isolated and if all the six channels are used additional decoding circuitry may be added.

The miser output is fed to a 30 Hz low pass filter 42 since the fised local oscillator frequencies on the time division multiplex system are each set at Fs+25Hz. A detector 44 detects the output of the filter 42 and its output is fed to each of a series of gates D0, 52, 54, 56 (plus two optional channels if fitted) wherein it is gated with the respective output of sequencer 36.

Each gate output 50 -- 56 is fed to a monitoring section 60 comprising two counters 62, 64 an AND gate 66 and three latches 68, 70, 72 which respectively give latched outputs indicating SIGNAL FAILURE; LIVE and ALARM to a logic circuit 80. Indicators 82, 84, 86 and 88 for channels 1 to 4 and an alarm indicator 90 are provided and are illuminated as indicated in Table 2. (An optional buzzer 92 may be provided and may be isolated by switch 94 if required).

TABLE 2 LAMP INDICATIONS CHANNEL CHANNEL ALARM CONDITION LAMP LAMP QUIESCENT OFF OFF LIVE CONTINUOUS OFF ALARM FLASHING CONTINUOUS LOSS OF SIGNAL FLASHING FLASHING Thus the system can indicate any condition for any channel (or premises).

The system operation is summarised as follows: The system consists of a number (up to 6 max.) of identical, but not interdependent, units 10 which communicate to each other the security status of their respective sites. Interconnection is by the common 2-wire line (of almost any type) L1 - L4.

Each unit 10 transmits information based on its condition (Quiescent/Live) and on the status of the security circuits feeding into it.

Each unit 10 receives and monitors information (including its on) on the common line and indicates this by means of the Channel and Alarm lamps and Audio Warning device 82 - 92. The indication (per channel) are QUIESCENT, LIVE, SECURITY ALARM or SIGNAL FAIL (the latter indicating cutting of the line or unit malfunction) as indicated in TabLe 2.

The Transmit section of each unit takes its inputs from site security circuits. Separate inputs are provided for Normally Open and Normally Closed circuits. The switch 28 selects the Quiescent or Live state; the Alarm circuitry being operative in either of these conditions.

Each unit transmits a discrete Audio frequency as follows : - 1) Quiescent : 3 second burst every 48 seconds 2) Live : 3 second burst every 24 seconds 3) Security Alarm: Continuous The Quiescent and Live patterns are derived from a Master Oscillator 32, via dividing and gating circuitry 30.

Any input alarm is latched by latch 20.

The Receive section of each unit searches, on a Time Division Multiplex basis, the Line Input for any of the six possible audio frequencies. The Line signals are fed to the input of a balanced Mixer 40. The Local Oscillator frequency for the Mixer 40 is derived from the Master Oscillator via a Programmable Divider 34. The Divider is controlled by a Sequencer 36 ( -: 6 counter) which steps every 250 mS. At each step, due to an appropriately selected division factor, the L.O. frequency is 25 Hz awas from one of the transmitted audio frequencies as specified in Table 1.

The Mixer output is fed via the 30 Hz Low Pass Filter AS to detector 44. The detector A l output pulse is gated in turn (under the control of the Sequencer) to an appropriate Pulse Counting dircuit 60. There are six such identical circuits, assigned to individual channels.

Since gating to each Channel occurs at 1.5 second intervals, a 3-second transmission will result in 2 pulses being applied to the relevant Pulse counting circuit. This provides a safety factor against poor transmission.

Constant transmission (ALARM) will result in a continuous pulse train of 1.5 sec. periodicity.

Each Pulse Counting circuit consists of: 1) Counter 62, which is Clocked at 10-second intervals and Reset by incoming pulses appropriately gated to it.

If the Channel is in the LIVE mode (pulses every 24 seconds), the Counter will only proceed to Count 2 or 3 before being Reset by an Input Pulse. Such coincidence SFTS the LIVE latch.

If the Channel is in the QUIESCENT mode (pulses every 8 seconds), the Counter will reach count 4 or 5 before being Reset b an incoming pulse, and in doing so, will RESET the LIVE latch.

If the Counter reaches Count 8 (i.e. no Input Pulse for at least 80 seconds) the SIGNAL FAIL latch is SET.

2) Counter 64, which is Clocked by incoming pulses and Reset every 10 seconds. If Count 4 is reached, the AL.ARFI latch is SET.

An Indicator lamp is associated with each Pulse Counting circuit. These lamps are Green (except for the Home Channel, which is .Amber) and are controlled by the state of the 3 iatches.

If the LIVE latch is Set, the Channel lamp is ON rontinuously. If either of the other latches are Set, the Channel lamp flashes at a 1 Hz period. (The ALARM condition takes precedence over all others).

Additionally, via further logic circuitry, all individual Pulse Counting circuits are commoned to a Red ALARM lamp 90 which operates as follows:1) Any SIGNAL FAIL latch SET - ALARM lamp flashes at 1 Hz period.

2) An ALARM latch SET - ALAR! lamp is ON continuously.

An Audio Warning device 92 (optional via switch) duplicates the perrormance of the ALARM lamp.

All latches, both in Transmit and Receive sections (with the exception of the LIVE latch, which is automatically Reset) are RESET b a RESET button.

Links are provided to permit the disablement of any of the Pulse Counting circuits (to cover maintenance, not required, etc.)

Claims (10)

1. CLAIMS 1. A security alarm system comprising an electronic control including transmission and receiving sections the transmission section serving to transmit an alarm condition to neighbouring premises to alert the occupants thereof and the receiving section serving to receive alarm conditions from one or more neighbouring premises to indicate an alarm condition within such premises.
2. 2. A securing alarm system as claimed in Claim 1 in which the electronic control circuitry includes means for identifying and indicating which of a plurality of premises is transmitting an alarm or other condition.
3. 3. A security alarm system as claimed in Claim 1 or Claim 2 in which the electronic controls in the premises are connected by a simple 2 wire link.
4. 4. A security alarm system as claimed in Claim 3 in which the electronic control circuitry includes means for detecting any disconnection of the link.
5. 5. A security alarm system as claimed in any preceding claim in which the system is provided with a back up battery system such that disconnection of the mains power does not disable the system.
6. 6. A security alarm system as claimed in any one of Claims 1 to 5 in which signals are transmitted at all times the signals being of three types respectively to indicate a quiescent condition of the system, a live condition and a security alarm condition.
7. 7. A security alarm system as claimed in Claim 6 in which in the quiescent condition a signal comprising a burst of frequency is transmitted every X seconds in which in the live condition a signal comprising a burst of frequency is transmitted every Y second wherein Y is substantially less than X and in which in the alarm condition a signal comprising a continuous frequency is transmitted.
8. 8. A security alarm system as claimed in Claim 7 dn.

   which the three signal types are detected by each receiver and decoded to indicate the condition of each transmitter.
9. 9. A security alarm system as claimed in Claim 8 in which a signal failure is also detected.
10. 10. A security alarm system substantially as described with reference to the accompanying drawings.