GB2228120A

GB2228120A - Intruder alarm system disarmed by radio signal

Info

Publication number: GB2228120A
Application number: GB8903105A
Authority: GB
Inventors: Nigel Stafford Mark Day
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-02-11
Filing date: 1989-02-11
Publication date: 1990-08-15
Also published as: GB8903105D0

Abstract

A radio (or other form of electromagnetic signal) receiver is included in an intruder alarm system, or added to an existing intruder alarm system, such that on receiving the signal from an associate transmitter it causes the alarm system to become 'disarmed'. When the radio receiver cannot detect the signal from the transmitter it causes the alarm system to become 'armed'.

Description

INTRUDER ALARM SYSTEM DISARMED BY RADIO SIGNAL This invention relates to an intruder alarm system that becomes disarmed whenever the signal from the portable transmitter is detected.

To highlight the shortcomings of conventional intruder alarm systems it is necessary to briefly describe the operation of such a system.

Example : A vehicle is fitted with an alarm system comprising; siren, control unit and sensor positioned to detect movement within the vehicle. On leaving the vehicle the operator has to 'set' the system by operating a switch with a key. The system now allows the operator 30 seconds to remove the key, leave the vehicle and shut the door. (If this not done within the time a tone will sound indicating that the sequence must be restarted within a further timed period or the siren will sound). When the 30 seconds has elapsed the system becomes 'armed'. On re-entering the vehicle the operator will be detected by the sensor. The system will sound a tone indicating that the operator has 30 seconds to insert the key in the control unit and 'disarm' the system. The control unit allows the siren to sound for a maximum time period of five minutes or until silenced by operating the keyswitch.

The drawbacks of such a system are The operator needs to find and use the key every time he/she leaves or enters the vehicle.

The operator has a limited time to gather belongings and leave the vehicle once the alarm is 'set'.

With the system 'armed', a person entering the vehicle will be detected by the sensor. Since the system is unable to differentiate between the operator and an intruder it will sound the normal entry tone for 30 seconds before sounding the siren. This is ample time to remove an item of value and be well away from the vehicle before the siren sounds.

There are many types of intruder alarm systems available for use in vehicles and buildings, many of which operate in this or a similar way. The aforementioned drawbacks can often mean that the system is left 'disarmed' when the operator is leaving and entering the vehicle/building frequently or for only a short time.

This invention provides an intruder alarm system or an addition to an existing alarm system such that it includes a radio (or other frequency of electromagnetic signal) receiver capable of receiving a signal from an associated radio transmitter. The receiving of the signal causes the alarm system to become 'disarmed'. The alarm system becoming 'armed' whenever it cannot detect the signal from the transmitter.

A specific embodiment of the invention will now be described by way of example.

A vehicle is fitted with an alarm system comprising ; a portable radio signal transmitter, a siren, control unit and a sensor positioned to detect movement inside the vehicle. The control unit has its 'arming/disarming' circuitry connected to a radio receiver. When the receiver detects the signal from the portable radio transmitter it causes the alarm to becomes 'disarmed'. The absence of this signal causes the system to become 'armed'. The strength of the transmitted signal (or the ability of the receiver to receive it) is adjusted to give a certain range at which the received signal is no longer strong enough to keep the system 'disarmed'.

The operator leaves the vehicle, taking with him the transmitter which is continuously emitting the signal required to 'disarm' the system. When the transmitter is sufficiently far from the receiver its signal will not be strong enough to keep the system 'disarmed'. The alarm system will thus become 'armed'. When the operator (with transmitter) returns, the transmitted signal will once again become sufficiently strong to disarm the system, thereby allowing the operator to enter the vehicle.

When the transmitter is out of range, causing the system to become armed, entry to the vehicle will cause the siren to sound immediately. The siren will continue to sound until a set period has elapsed or the transmitter comes within range of the receiver.

The transmitter can take the form of a pocket-sized unit powered by a rechargeable battery. The signal it produces maybe of a specific frequency and/or coding and/or duration to match that required by the receiver in order to operate.

To extend battery life between charges the transmitter may be arranged to transmit intermittently (with the receiver arranged to accept this).

The receiver may be arranged to respond only to a signal matching that produced by the transmitter.

The receiver may be arranged to cause the alarm system to sound the siren if a signal is received that is similar in its parameters although still incorrect.

To prevent 'disarming/arming' switching when the transmitter is either partly shielded or at the limit of its range the receiver may be arranged to 'arm' the system only when it has received the appropriate signal for a certain timed period.

Claims

1. An intruder alarm system or an addition to an existing alarm system such that it includes a radio (or other form of electromagnetic signal) receiver capable of receiving a signal from an associated radio transmitter. The receiving of the signal causes the alarm system to become 'disarmed'. The alarm system becoming 'armed' whenever it cannot detect the signal from the transmitter.

2. An alarm system or addition as described in claim 1 whereby the radio signal produced by the transmitter is of a specific frequency and/or coding and/or duration.

3. An alarm system or addition as described in claims 1 and 2 whereby the receiver is arranged to respond only to a signal matching that produced by the transmitter.

4. An alarm system or addition as described in claim 1 whereby the radio receiver is arranged to cause the alarm system to sound the siren if the signal received is similar in its parameters to that produced by the transmitter but not the same.

5. An alarm system or addition as described in claim 1 whereby the receiver is arranged to 'disarm' the alarm system only when it has received the signal from the transmitter for a certain length of time.

6. An alarm system or addition as described in claim 1 whereby the transmitter is arranged to transmit intermittently in order to reduce the average power consumption.

7. An alarm system or addition as described in claim 1 whereby the transmitter is a portable pocket-sized unit.

8. An alarm system or addition as described in claim 1 whereby the transmitter is powered by a rechargeable power source.

9. An alarm system or addition to an existing alarm system substantially as described herein.