Found in a publication by Gernsback from 1960, this circuit uses germanium transistors of the time and commercial coils. It can be changed to operate with modern transistors and other wavebands.
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...