GB2208558A - Security system - Google Patents

Abstract

A sensor in a burglar alarm system comprises an electrically conducting bridge 22 secured to an openable window light 24, electrically conducting leads 25 connected or connectible with the opposite ends of said bridge and anchored securely at a position 26 spaced from said bridge with a loop thereof therebetween whereby the circuit including said leads will be broken if the light is opened by more than a predetermined extent. The bridge 22 may be mounted on a piezoelectric break glass detector. <IMAGE>

Description

SECURITY SYSTEM This invention concerns a security system, particularly, though by no means exclusively, suitable for use in domestic premises.

Many kinds of burglar alarm system are known, those which summon aid by telephone or radio and those which act simply as a deterrent by activation of audio or visual alarm means. All rely upon intruder detecting sensors, be they mechanical switches in the form of door or window contacts or floor mats for example; or more sophisticated units such as passive infra-red, vibration or ultrasonic sensors for example.

It is becoming increasingly (and disturbingly) common for thieves to violate domestic dwellings when the owners are known to be in residence, since there is a largely justified assumption that at such times the alarm systems will be inoperative.

Many householders, particuarly of larger country properties, are nowadays relying on two separate alarm systems. One is intended to be armed, at least in part, when the premises are occupied and comprises so-called perimeter protection adapted to detect any attempted entry to the building at least through selected parts thereof. The other is intended to be armed when the premises are vacated, and will include sensors adapted to detect any intruder who has penetrated the interior of the building.

The first system necessarily makes use of vibration (sometimes called 'seismic') sensors, break-glass sensors and possibly other (for this is a continually developing art) types of sensor which can be active without seriously impeding normal living activity within the dwelling. They often, though, prevent normal operation of windows and external doors and anyway frequently include devices prone to failure and false-alarms, a particular problem in view ofsincreasing lack of sympathy from the authorities to such incidents - more frequently notified as neighbourly responsibility is enhanced through Home-watchw schemes and the like.

It is an object of this and a related invention, the subject of co-pending Patent Application No.

dealing with windows and external doors respectively, to provide a perimeter alarm system which can be armed when the protected premises are occupied without seriously inconveniencing normal living activity and with reduced risk of false alarm.

According to the present inventon there is provided a sensor in a burglar alarm system comprising an electrically conducting bridge secured to an openable window light, electrical conducting leads connected or connectible with the opposite ends of said bridge and anchored securely at a position spaced from said bridge with a loop thereof therebetween whereby the circuit including said leads will be broken if the light is opened by more than a predetermined extent.

The predetermined extent may be such as to permit adequate ventilation but insufficient to allow human ingress.

The bridge may terminate in a two-pin socket, the leads being connectible therewith by means of a complimentary plug.

The bridge may be secured to the openable window frame or to the glazing therein.

For added security the bridge may be mounted on a break-glass detector (preferably of the piezo-electric kind) itself secured to the frame or glazing.

The invention will be further apparent from the following description, with reference to the several figures of the accompanying drawings, which show, by way of example only, a number of sensors embodying same.

Of the drawings: Figure 1 shows a schematic circuit diagram of a burglar alarm system incorporating a sensor of the invention; Figure 2 shows a perspective view of part of an openable window light fitted with one form of sensor; and Figure 3 shows a view similar to that of Figure 2 but with an alternative form of sensor.

Referring firstly to Figure 1, it will be seen that the burglar alarm system comprises a control box 10 incorporating a key switch 11 which can be turned to an on-position to arm the system, cabling 12 to alarm means such as a bell, siren or telephone auto-dialling unit 14 which the system activates whenever an intruder is detected by a break in the normally closed ciruit 15 which includes sensor devices 16 each of which normally contributes to completion of the circuit 15.

These devices 16 may be many and of various kinds but at least one will be as shown in Figure 2.

The sensor of Figure 2 comprises an electrically conducting bridge comprised by a two-pin socket 20 whose two sides are permanently electrically connected and a two pin plug 21 breaking the circuit 15 but adapted to be engaged with the socket 20 to complete the circuit.

The socket 20 is secured by screws 22 or similar to the openable frame 23 of a window light 24.

The leads 25 joining the plug 21 to circuit 15 are anchored securely at a position 26 spaced from socket 20 with a loop thereof therebetween whereby if the light is opened by more than a predetermined extent the plug 21 will be pulled from the socket 20 to break circuit 15 and activate the alarm.

For added security and as shown in Figure 3 the socket 20 may be secured to the face of a break glass detector 30 (preferably of the piezo-electric kind) such that the pins of the socket are in series with the normally closed contacts of the detector 30. The detector 30 is secured to the glazing 31 of the light.

This gives added protection activating the alarm by attempted ingress by breaking the glass or opening the surrounding frame.

It will be appreciated that it is not intended to limit the invention to the above example only, many variations, such as might readily occur to one skilled in the art, being possible, without departing from the scope thereof.

Thus, for example, switch means may be associated with the plugs to enable a short circuit between their pins permitting full opening of the window for cleaning or other purposes, again the socket need not be fixed to the window or frame but rather located in a support bracket member from which it may be removed, again permitting opening of the window without activation of the alarm. This latter arrangement is particularly suitable for use on patio windows or patio doors.

Claims (9)

1. A sensor in a burglar alarm system comprising an electrically conducting bridge secured to an openable window light, electrical conducting leads connected or connectible with the opposite ends of said bridge and anchored securely at a position spaced from said bridge with a loop thereof therebetween whereby the circuit including said leads will be broken if the light is opened by more than a predetermined extent.

2. A sensor according to claim 1 wherein the predetermined extent is such as to permit adequate ventilation but insufficent to allow human ingress.

3. A sensor according to claim 1 or claim 2 wherein the bridge terminates in a two-pin socket, the leads being connectible therewith by means of a complementary plug.

4. A sensor according to claim 3 including switch means to enable a short circuit between the pins of said plug to enable the plug to be removed from the socket without breaking said circuit.

5. A sensor according to any preceding claim wherein the bridge is secured to a frame of the openable window.

6. A sensor according to any one of claims 1-3 wherein the bridge is secured to the glazing in the openable window frame.

7. A sensor according to any preceding claim wherein the bridge is mounted on a break-glass detector itself secured to the frame or glazing.

8. A sensor according to claim 6 wherein the break-glass detector is of the piezo-electric kind.

9. A sensor according to any preceding claim wherein the bridge is located in a support bracket from which it may be lifted to permit opening of the window light without breaking said circuit.