GB2318461A

GB2318461A - Burglar deterrent

Info

Publication number: GB2318461A
Application number: GB9621707A
Authority: GB
Inventors: Raymond Cumberland
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-10-18
Filing date: 1996-10-18
Publication date: 1998-04-22
Also published as: GB9621707D0

Abstract

A burglar deterrent has means for varying the intensity of light emitted from a source 16 at irregular intervals to simulate the illumination provided by a television receiver. A random number generator 10 may be connected to a timing circuit 12 which remains in a given state for a period dependent on the output of generator 10, such period typically being in the range 1 to 15 seconds. At the end of each such period, an intensity control circuit 14 sets a new randomly selected intensity level depending on a signal from generator 10. The source 16 may give a blue light. Alternatively, colour and intensity may be changed at irregular intervals by use of a movable filter or by use of a plurality of different coloured bulbs. A timer may be provided so that the apparatus operates at predetermined times of day.

Description

Burglar Deterrent The present invention relates to a burglar deterrent.

Electrical devices are known that are designed to give the impression to a would be burglar that a house is occupied. Hence, time switches are known for automatically opening operating lights in a house or for automatically opening and closing curtains.

According to the present invention, there is provided a burglar deterrent that comprises a light source having means for varying the intensity of the emitted light at irregular intervals to simulate the illumination provided by a television receiver.

Preferably, the light source should emit a coloured light to simulate a colour television receiver.

If desired, the colour of the emitted light may be changed at irregular intervals as well as the light intensity.

Changes in intensity and colour can be achieved by the use of a movable filter but it is preferred to vary the current supplied to a light bulb. To change colour, it is possible to vary the relative intensity of the light emitted from two or more coloured light bulbs. If the burglar deterrent is designed to be plugged into a mains socket, the intensity of the light can be varied using a thyristor control circuit, as used in conventional dimmers.

In order to simulate the periodicity of the changes in the light output of a television receiver in which scene changes are random, the light intensity should also be changed in a random manner.

As the intention is to simulate a television receiver, each intensity should be held for a period of preferably between 1 and 15 seconds.

The light source can be controlled by a microprocessor that is either programmed to generate random numbers or has a table of pseudo-random numbers stored in memory.

Alternatively, a dedicated analogue or digital circuit may be used to vary the emitted light intensity in a random manner. Pseudo-random number generators can for example be produced using a shift register connected in a closed loop with the input receiving the sum of signals prevailing at different stages of the shift register.

If desired, a timer may be built into the burglar deterrent so that it should automatically operate at preset times of the day.

The invention will now be described further, by way of example, with reference to the accompanying drawing which is a block diagram of a burglar deterrent of the invention.

The outer appearance of the deterrent may be the same as a convention darkroom light. Hence, it may comprise an opaque housing containing a light bulb with a window in one wall. The light emitted by a television has a generally blue hue and it suffices to use a light blue filter or a light blue filter in the window to simulate the illumination of a television without resorting to the complexity of changing the hue of the emitted light. Of course, if changes in hue are required, then they can be achieved by using bulbs of different colour and varying their intensity independently.

The circuit used to vary the intensity comprises a random number generator 10 and a variable timing circuit 12 that remains in any given state for a period of time between typically 1 and 15 seconds, depending on the signal received from the random number generator. At the end of the period, a signal is applied to an intensity control circuit 14 that sets a new randomly selected intensity level depending on a signal received from the random number generator 10 and controls the light source 10 accordingly until the next command is received from the timing circuit 12.

The circuit described above can be implemented in hardware or by programming a microcomputer. Numerous analogue and digital circuits will be apparent to the person skilled in the art for randomly varying the intensity of the light emitted by a light source without the need for further detailed explanation.

It is convenient to incorporate a timer so that the burglar deterrent may operate automatically at preset times.

Claims

1. A burglar deterrent comprising a light source having means for varying the intensity of the emitted light at irregular intervals to simulate the illumination provided by a television receiver.

2. A burglar deterrent as claimed in claim 1, wherein the light source emits a coloured light to simulate a colour television receiver.

3. A burglar deterrent as claimed in Claim 1 or 2, wherein changes in intensity are achieved by varying the current supplied to a light bulb.

4. A burglar deterrent as claimed in any preceding claim, wherein the colour of the emitted light is changed in use at irregular intervals as well as the light intensity.

5. A burglar deterrent as claimed in claim 4, in which the colour of the emitted light is changed by varying the relative intensity of the light emitted from two or more coloured light bulbs.

6. A burglar deterrent as claimed in any preceding claim, wherein the intensity of the emitted light is maintained constant for periods of random duration ranging between 1 and 15 seconds.

7. A burglar deterrent as claimed in any preceding claim, wherein the light source is controlled by a microprocessor that is programmed to generate random numbers or has a table of pseudo-random numbers stored in memory.

8. A burglar deterrent as claimed in any preceding claim, wherein a timer is built into the burglar deterrent to operate it automatically at preset times of the day.

9. A burglar deterrent constructed, arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.