Improvements in anti-theft systems

摘要

1,079,028. Theft alarms. ELECTRO-PRECISION S.A. Nov. 6, 1964 [Nov. 8, 1963; Oct. 27, 1964], No. 45346/64. Heading G4N. A theft alarm, e.g. for a vehicle comprises a relay RT3 connected in series with an alarm detector D1 and a parallel arrangement of three further relays RT1, R2, RT2 so arranged that RT1 operates first. On leaving the vehicle a concealed switch (not shown) is actuated to connect terminal 6 to the battery and thermal relay RT3 starts to heat up, the delay time before contacts RT31 dose being sufficient to allow the driver to leave the vehicle via the door including alarm detector D1. Once contacts RT31 have closed subsequent closure of detector contacts D1, by opening the door, energize relay R1 to close self-hold contacts R11. Thermal relay RT1 starts to heat via its winding a and after a sufficient delay to allow an authorized person to immobilize the alarm, contacts RT11 close, de-energizing relay R1 and energizing relay R2 to close alarm contacts R21, R22, R23 and selfhold contact R24. Thermal relay RT2 also starts to heat and after a delay time contacts RT21 close, releasing relay R2. RT2 now cools until it contacts RT21 open, relay R2 reoperates and the cycle repeats. After a much longer delay period relay RT1 is released by the heater winding b and the whole system is switched off. If the detector originally set off does not return to normal the system starts up again to repeat the cycle. Other detectors e.g. D2 are connected so as to actuate relay R2 directly without any delay. In a modification, Fig. 2 (not shown), detector (D1) is connected to terminal (1) via a resistor, detector (D2) is directly connected to terminal (1), and a further resistor is included in lead (16). Instead of a winding (b) resistor (RA) may provide the heat to release relay (RT1) directly.