Leak Detector (CB22456E)

We found this circuit in a Popular Electronics from 1992. The transistor is general purpose, assuming equivalent.

200 Hz to 400 Hz Band Pass Filter (CB13603E)
We found this circuit in a 1975 filter cookbook. The circuit can use other operational amplifiers and...
Guitar Intensifier (CB11507E)
The purpose of this circuit found in a Popular Electronics from 1972 is to intensify certain...
Mini MW Transmitter (CB10307E)
This circuit was found in a 1964 magazine, which no longer exists. It is a small wireless...