Intercom (CB21660E)

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

100 kHz Tunnel Diode Oscillator (CB1335E )
This basic oscillator with tunnel diode generates a 100 kHz signal with 1 uW output power. The...
Headphone Amplifier (CB14463E)
This amplifier for medium or high impedance magnetic headsets (above 200 ohms) was found in an...
Crystal Time Base (CB19368E)
This circuit provides precise signals of three frequencies, using CMOS technology. The integrated...