GB1357262A - Anti-hijacking vehicular alarm system - Google Patents

Abstract

1357262 Vehicle alarm systems ITAD ALARM SYSTEMS Inc 5 Jan 1972 462/72 Heading G4N In a hijacking alarm system for a vehicle, a timer is set by the driver to the estimated time of the journey and during this period an alarm is given if a door of the vehicle is opened or if an attempt is made to nullify the alarm or alter the time period. As shown, the alarm system is inhibited by opening a key-operated switch 20, the key of which is retained at the vehicle's terminal. A further key-operated switch 22 for operation by the driver is mounted within a control box (Figs. 2-4, not shown). Protection of parked vehicles.-When the driver switch 22 is set to the righthand position, the ignition circuit 50 is short-circuited and a relay 54 is operable by movement of the vehicle, as detected by a mercury switch 60. Relay 54 operates a siren 12. Hijacking alarms.-When the driver switch 22 is set to the lefthand position, a relay 30 is energized by switches 14 or 16 on opening a door of the vehicle, relay 30 operating the siren 12 for a period determined by a timer 44. When the driver wishes to enter the vehicle he closes a key-operated IN switch 68 (accessible from outside the vehicle) which energizes a relay 74 thus disconnecting the door switches 14, 16. The driver then reopens the IN switch 68 so that relay 74 is released when the door is closed. A similar key-operated OUT switch 70 is included to allow departure from the cab. The alarmoperating relay 30 would now be energized by movement of the vehicle as detected by a mercury switch 80. This is inhibited for the estimated duration of the vehicle's journey by setting a clockwork timer by means of a control 92 contained within the lid of a control box (Figs. 2-4, not shown). When the timer is set, mercury switch 80 is inhibited by contacts 82; contacts 98 bring into circuit a tamper switch 100 and a key-operated trap look switch 102 also contained in the control box. Switch 102 is operated by the same key as the IN and OUT switches 68, 70 and is closed by removal of the key. During the preselected time period, opening of a vehicle door, adjustment of the timer or tampering with the control box will actuate the siren 12. Five minutes before the completion of the journey, a bell 120 is operated and a further bell 122 is operated when the time period has elapsed and contacts 82, 98 are restored to the position shown. The driver can then remove the key from the trap lock switch 102 and depart from the vehicle by closing the OUT switch 70.