This shield circuit is from a 1968s Motorola documentation. The relay is according to the supply voltage. R1 can be reduced to lower trigger voltages.
This circuit, suggested by National Semiconductor, provides an output voltage proportional to the...
This powerful alarm circuit was found in the July 1975 issue of Radio Electronics magazine. The...
This two-transistor circuit was found in the January 1994 issue of Electronics Now magazine....