Intercom (CB21660E)

This good gain circuit was found in a Popular Electronics from April 1967. The transistors are germanium of the time.

High Input Voltage Regulator (CB13050E)
The 78XX series voltage regulator integrated circuits do not support an input voltage greater than...
Multimeter Circuit (CB23623E)
This is the complete circuit of a multimeter using a 50 uA instrument with a 2k coil. The circuit...
1kHz Double T Oscillator (CB10957E)
This circuit came out in a Popular Electronics from December 1995. It is a double T configuration that...