This circuit is from an American manual from 1975. The transistors are types of the time, but equivalents can be used, as well as the relay that can be according to the supply voltage.
This circuit is from a documentation from the 70s. The transistors are types of germanium of the...
This filter has the components calculated for the frequency of 1 kHz but can be changed. The input...
We found this conventional receiver circuit in a 1990 documentation. The circuit includes an audio...