Found in an American circuit manual from the 1970s, this circuit can use any general-purpose transistor. The operating frequency range is from 600 to 4000 Hz.
This circuit is from the 1993 Motorola Linear Interface Circuits. The source does not have to be...
This range is normally used in marine communications as indicated in the 1989 documentation. The...
This shield circuit is from a 1968s Motorola documentation. The relay is according to the supply...