IE69055B1 - A method and apparatus for alerting to the presence of a jamming signal - Google Patents

Description

The present invention relates to a method and apparatus for alerting a user of a vehicle alarm of the type comprising a receiver for receiving a transmitted arming and disarming signal to the presence of a transmitted jamming signal.

Vehicle alarms, typically, car alarms of the type which are armed and disarmed by a transmitted signal, generally, a radio signal, in general comprise a receiver for receiving the radio signal. The radio signal is normally transmitted from a remote hand held transmitter, which, in general, on being activated transmits a unique radio signal which is identifiable to the receiver. On receipt of the signal, the state of the car alarm is changed, for example if the car alarm is armed, receipt of the signal disarms the alarm and vice versa.

Various methods are known to car thieves which enable the disarming of’ certain car alarms which have already been armed. Recently, car thieves have begun to adopt a method which prevents the arming of a car alarm in the first instance. Such methods require the transmission of a jamming signal in the near vicinity of the car, which prevents clear reception of an arming signal by the car alarm, thus rendering it impossible ' for a user to arm the alarm. The user, being unaware I of the presence of the jamming signal, in general will 5 assume the car alarm to be faulty and will leave the car locked with the alarm disarmed. Accordingly, a thief can readily easily steal the car.

There is therefore a need for a method and apparatus for alerting a user of such a car alarm to the presence of a jamming signal. The present invention is directed towards providing such a method and apparatus.

According to the invention, there is provided a method for alerting a user of a vehicle alarm of the type comprising a receiver for receiving a transmitted arming and/or disarming signal to the presence of a transmitted jamming signal, the method comprising the steps of: reading a signal received by the receiver, comparing the read signal with a reference signal, if the read signal is dissimilar to the reference signal, then after a period of time, reading a « subsequent signal received by the receiver, comparing the subsequent signal with the reference signal, and if the subsequent signal is still dissimilar from the reference signal, alerting the user to the presence of a jamming signal.

Preferably, the subsequent signal is read after a predetermined period of time.

Advantageously, the alerting means is a siren or light of the vehicle, and the method comprises the step of activating the siren or light in a predetermined pattern.

Additionally, the invention provides apparatus for 10 alerting a user of a vehicle alarm of the type comprising a receiver for receiving a transmitted arming and/or disarming signal to the presence of a transmitted jamming signal, the apparatus comprising: a reading means for reading a signal received by 15 the receiver, a comparing means for comparing the read signal with a reference signal, a timing means for timing a period of time, the timing means being responsive to the comparing means identifying the read signal as being dissimilar to the reference signal, the reading means being responsive to the timing means for reading a subsequent signal subsequently received by the receiving means after the timing means has timed the period of time for comparison with the reference signal by the comparing means, and an activating means responsive to the comparing means for activating an alerting means to alert a user to the presence of a jamming signal.

Preferably, the timing means times a predetermined period of time between the times that signals are read from the receiving means. Advantageously, the activating means comprises a driver for operating the alerting means in a predetermined pattern.

The invention will be more clearly understood from the following description of a preferred embodiment thereof, which is given by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a block representation of a car alarm according to the invention, and Fig. 2 is a flow chart of a sub-routine of a computer programme which controls the car alarm. ή Referring to the drawings, there is illustrated in 20 block representation a circuit of a car alarm according to the invention indicated generally by the reference numeral 1. The car alarm comprises a main controller, namely, a microprocessor 2 for controlling the operation of the car alarm. An output 3 of a radio receiver 4 is connected to a port 5 in the microprocessor 2 which reads signals from the output 3 received by the receiver 4. A port 6 of the microprocessor 2 receives signals from sensors, typically, ultrasonic sensors 7 mounted in the car for monitoring the presence or absence of air movement in the car for detecting a thief. A relay driver 8 is connected to a port 9 of the microprocessor 2, and is controlled by the microprocessor 2 for activating an alerting means, which typically may be a siren 10 in the car or lights 11 of the car. A port 12 is provided from the microprocessor on which a signal is provided for operating a relay driver 14 which may be connected to a central locking system of the car for centrally locking the car, to the ignition of the car for disabling the ignition or to other features of the car for immobilisation thereof.

In normal use, the receiver 4 receives a transmitted signal from a remote transmitter for arming and disarming the car alarm 1. The microprocessor 2 under the control of a main computer programme reads the output 3 of the receiver 4 at predetermined intervals to establish the presence of a radio signal. On the presence of a radio signal being established, the computer programme compares the read radio signal with a reference signal. Should the read signal and reference signal be similar, the state of the car alarm is changed. In other words, if the car alarm is in the disarmed state, the microprocessor arms the car alarm and vice versa. On arming of the car alarm, a signal is applied to the port 12 for immobilising and/or locking the car. A signal is also applied to the port 9 for briefly activating the siren and/or lights to indicate to the user that the alarm has been armed. On disarming of the alarm, the procedure is reversed. In the event of a signal being received on the port 6 of the microprocessor 2 from an ultrasonic sensor 7 caused by air movement in the car, a signal under the control of the main computer programme is applied to the port 9 of the microprocessor 2 for activating the relay driver 8 for operating the siren and/or lights of the vehicle.

Referring now to Fig. 2, the flow chart of a subroutine of the main computer programme for operating the microprocessor 2 and in turn the car alarm 1 for alerting a user to the presence of a jamming signal will now be described. Block 20 of the sub-routine comprises a reading means, which reads the output 3 of the receiver 4, after which the sub-routine moves to block 21. Block 21 checks for the presence of a signal on the output 3. If a signal is not present on the output 3, block 21 returns the sub-routine to block 20. If block 21 determines that a signal is present on the output 3, the sub-routine moves to block 22, which comprises a comparing means which compares the read signal from the output 3 with a stored reference signal to establish if the read signal is a valid signal for arming or disarming the car alarm 1. Should block 22 determine that the signal read from the output 3 is a valid signal, the sub-routine moves to block 23 which returns control of the microprocessor 2 to the main computer programme for changing the state of the car alarm.

Should block 22 determine that the signal read on the output 3 is not a valid signal, the sub-routine moves to block 24 which activates a timing means, namely, a timer in the microprocessor 2 to time a predetermined period of time, which in this case is approximately ten seconds. On block 24 having timed out the ten second predetermined period, the sub-routine moves to block 25 which reads the output 3 of the receiver 4, and the sub-routine moves to block 26 which checks for the presence of a signal, in other words, a subsequent signal on the output 3. Should block 26 determine that a signal is not present on the output 3, the subroutine returns to block 20. If block 26 determines the presence of a subsequent signal on the output 3, the sub-routine moves to block 27 which compares the just read subsequent signal with the stored reference signal to establish if the subsequent signal is a valid signal for arming or disarming the car alarm 1. Should block 27 determine that the signal read from the output 3 is a valid signal, the sub-routine moves to block 23. Should block 27 determine that the just received signal is not a valid signal, the sub-routine moves to block 28 which activates the siren 10 in a predetermined identifiable pattern by applying a signal on the port 6 of the microprocessor 2 which causes the relay driver 8 to operate the siren 10 to give six regular equi-spaced bleeps of the siren. This thus indicates the presence of a jamming signal to the user. The user may then either continue to attempt to arm the car alarm, or alternatively may move the car to an alternative parking space out of range of the jamming signal. The sub-routine moves to block 29 from block 28 which returns control of the microprocessor to the main computer programme.

The invention is not limited to the embodiment hereinbefore described which may be varied in detail.

Claims (9)

1. A method for alerting a user of a vehicle alarm of the type comprising a receiver for receiving a transmitted arming and/or disarming signal to the presence of a transmitted jamming signal, the method comprising the steps of: reading a signal received by the receiver, comparing the read signal with, a reference signal, if the read signal is dissimilar to the reference signal, then after a period of time, reading a subsequent signal received by the receiver, comparing the subsequent signal with the reference signal, and if the subsequent signal is still dissimilar from the reference signal, alerting the user to the presence of a jamming signal.

2. A method as claimed in Claim 1 in which the subsequent signal is read after a predetermined period of time.

3. A method as claimed in Claim 1 or 2 in which the alerting means is a siren or light of the vehicle, and the method comprises the step of activating the siren or light in a predetermined pattern.

4. A method for alerting a user of a vehicle alarm of the type comprising a receiver for receiving a transmitted arming and/or disarming signal to the presence of a transmitted jamming signal, the method being substantially as described herein with reference to and as illustrated in the accompanying drawings.

5. Apparatus for. alerting a user of a vehicle alarm of the type comprising a receiver for receiving a transmitted arming and/or disarming signal to the presence of a transmitted jamming signal, the apparatus comprising: a reading means for reading a signal received by the receiver, a comparing means for comparing the read signal with a reference signal, a timing means for timing a period of time, the timing means being responsive to the comparing means identifying the read signal as being dissimilar to the reference signal, the reading means being responsive to the timing means for reading a subsequent signal subsequently received by the receiving means after the timing means has timed the period of time for comparison with the reference signal by the comparing means, and an activating means responsive to the comparing means for activating an alerting means to alert a user to the presence of a jamming signal.

6. Apparatus as claimed in Claim 5 in which the timing means times a predetermined period of time between the. times that signals are read from the receiving means.

7. Apparatus as claimed in Claim 5 or 6 in which the 5 activating means comprises a driver for operating the alerting means in a predetermined pattern.

8. Apparatus for alerting a user of a vehicle alarm of the type comprising a receiver for receiving a transmitted arming and/or disarming signal to the

9. 10 presence of a transmitted jamming signal, the apparatus being substantially as described herein with reference to and as illustrated in the accompanying drawings.