Flood alarm (CB7994E)

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

Mechanical Reverb (CB23788E)
This reverb effect was found in the December 1961 Radio Electronics magazine. It makes use of...
1 to 20 MHz Colpitts Oscillator (CB6506E)
Found on Popular Electronics from the 1990s, this oscillator uses a general purpose transistor. The...
High Pass Filter (CB25602E)
This simple 741 circuit was found in the August 1993 Electronics Now magazine. The source must be...