Testing of thermistors and SCRs (CB21391E)

This circuit was found in an old American manual. It is intended for testing SCRs and thermistors using indicator lamps.

Triac dimmer (CB7857E)
We have dozens of similar projects in articles and circuits on this site. This is from Radio...
Super regenerative detector (CB24292E)
This circuit with an unusual configuration was found in the January 1974 issue of Radio...
Low Voltage Regulator (CB6406E)
This interesting circuit from 1967 documentation uses three series lamps to regulate the voltage...