This circuit appears on this site from different sources. This is from documentation from the 1980s. The operating system used is uncommon and can be replaced by a more modern equivalent.
This circuit is indicated for audio tests, the tracks being selected by the capacitors. The...
This passive circuit was found in a 1980s documentation. The circuit serves to indicate the...
This small 3 transistor transmitter was found in an English publication from 1963. The coils must...