This commercial circuit is from a Japanese magazine from 1967. It uses germanium transistors, and the coil can be made with 80 to 100 turns of fine enameled wire on a ferrite rod.
Found in a 1964 Electronic Design, this circuit shows how to modulate a signal with a dynamic low...
This circuit is from an 80's documentation, firing when the input voltage exceeds 5 V. The SCR can...
The transistor used is one of the first power Darlingtons with a collector current of 3 A. The...