Diode Tester (CB22137E)

This diode tester was found in an English publication from the 1980s. Transistors are general-purpose types of the time.

Video Modulator (CB14572E)
The circuit shown is from Motorola's 1990 Linear Databook. Shaded components are optional. The...
Biestable Touch Switch (CB10246E)
This circuit is from an English magazine of 1977. The circuit is still current, just using BC547...
Microphone Preamplifier (CB10228E)
This circuit is from a 1986 Revista Española de Electrónica. It consists of an amplifier with...