This circuit is for traditional old-style telephone lines found in an American 1980s documentation. Components are common and the optical coupler can be replaced with an equivalent.
The search coil of this detector consists of 140 turns of wire 18 in an 8 inch diameter form. The...
This circuit was obtained from a 1966 General Electric documentation. It can serve as a basis for...
The quiescent current of this alarm is in the order of microamps and the same is true for the...