Microphone Preamp (T871E)

This single-tube preamp stage was found in documentation from 1944. Note the supply voltage. The circuit is for crystal microphones.

100 Hz Fourth Order High Pass Filter (CB25819E)
This circuit was taken from an article in Electronics Now magazine in February 1995. The power...
Bistable relay (CB7159E)
Found in a Hands On Electronics from the 80's, this circuit activates a relay with alternating...
NPN and PNP Transistor Power Switch (CB992E)
This circuit was found in a publication of the year 1968. It uses complementary transistor to...