Flood alarm (CB7994E)

This circuit is from a 90s Popular Electronics. The transistors are of general use and the buzzer is a Sonalert type.

Unijunction Oscillator (CB4431E)
This is the traditional unijunction transistor relaxation oscillator circuit for the audio band. The...
4-channel system Amplifier (CB24168E)
This is half of a 4-channel amplifier from a system published in the October 1971 issue of Radio...
Crystal dipper and oscillator (CB23926E)
This circuit works both as a grid-dip (transistorized) and as an oscillator. The circuit is from a...