NPN and PNP transistor tester (CB22146E)

This simple transistor tester was found in old English documentation. Suitable for general purpose transistors.

Relay driver (CB9727E)
This traditional relay configuration, found in old documentation, is intended for 2A relays for...
Heterodyne frequency meter (CB21564E)
This circuit was found in a book on transistors from 1954. It works by the beat that is detected by...
4-Range DC Millivoltmeter (CB25228E)
Using an LF356 operational, this circuit was found in the September 1989 issue of Radio...