GB1404341A - Control device - Google Patents

Abstract

1404341 Vehicle theft alarms UM ELECTRICAL DISTRIBUTORS Ltd 29 July 1972 14815/72 Heading G4N In a control system for activating electrical apparatus such as a relay RL1, a latch 6, 7 provides "armed" and "disarmed" conditions such that, in the armed condition, the apparatus RL1 is operable by either of two activating signals (e.g. from LP1 and LP2) whilst, in the disarmed condition the apparatus RL1 cannot be activated. The system includes a bi-stable device 2, 3 and a timer C1, VR1 arranged to change the state of latch 6, 7 by specified combinations of activating signals being present or absent during a predetermined time period. Vehicle theft alarms.-A system is described in which the horn of the vehicle is sounded and the ignition immobilized if a door of the vehicle is opened when the system is armed. If a door, boot or bonnet of the vehicle is opened, a switch SW2 is closed, lighting lamp LP1 which irradiates photo-transistor LST1 which initiates a chain of gates 1, 2, 6, 5, 8 so as to turn on transistor T3 which energizes relay RL1. The relay is held energized by contacts SW6 for two minutes while capacitor C4 discharges via transistors T4, T5. Contacts SW4 of relay RL1 break the ignition circuit, contacts SW8 energize a flasher 30 which feed intermittent current to the horn via contacts SW8. A similar action occurs if the ignition switch SW3 is closed, since this lights lamp LP2 which irradiates photo-transistor LST2. Disarming.-The system is disarmed by momentarily changing over a key-operated switch SW1, this action charging C1 and discharging C2. A latch, formed by NAND gates 6 and 7 is reversed so that gate 6 gives a 0 which is passed by gates 5 and 8 to turn off T3. C1 begins to discharge via VR1 until latch 6, 7 changes over causing C2 to charge, thus rearming the system. If, however, a door is opened before C1 has discharged, SW2 closes and gates 1 ... 4 provide Is so that C1 is recharged via D1. Gate 5 does not change since C2 is still discharged. When the door is reclosed SW2 opens and C1 begins to discharge via VR1. If the ignition switch SW3 is closed before C1 has discharged (e.g. within 20 sees) gates 2 and 3 are reversed, C1 is recharged and this condition maintained until a door is opened. Re-arming.-When the ignition switch SW3 is opened, gate 4 gives a 1 and gate 3 remains on so that C1 remains charged via D2. When a door is opened, SW2 is closed so that gates 2 and 3 are reversed. On reclosing the door, gates 1 and 4 provide Os. C1 discharges until the latch formed by gates 6 and 7 reverse, thus re-arming the system. Bridge B 1 prevents a reverse voltage being supplied. Modifacationa.-SW6 may be manually set to its second position to provide a hijack alarm. SW4 may operate a valve in a compression ignition engine. It is mentioned that the device may be used for the protection of buildings or safes.