Car radio alarm

EE 84 July/August 1986 61car radio alarm 1 +12V +12V(DI • OV OV0 4,C(• It is an unfortunate as well as a gener- ally acknowledged fact that the car radio (plus cassette recorder) ranges among the most desirable and often surprisingly easy to steal objects on many a burglar"s "shopping list". This circuit may help to prematurely end the criminal practice by sound- ing the horn if it is attempted to remove the radio set; cutting or unplugging an additional ground wire, which has been hidden in the cable for connection to the battery and loudspeaker(s), causes the alarm to be set off, since the connection to the car chassis (ground) is inter- rupted. The circuit for the car radio alarm is Parts list Resistors: Rt=10 52 R2;R3= 100 k 84 = 1 k R5 = 10 k Capacitors: Ci =10 1.4;16 V electrolytic C2= 100 n;MKT C3= 100 p;25 V electrolytic Semiconductors: Di;D2;D4=1N4001 03= 1N4148 IC( =555 Miscellaneous: Ret =12 V coil; single changeover*. PCB 86406 (not available through Readers Servic...