Phone circuit (CB8709E)

With this circuit, found in a 80s Popular Electronics, it is possible to use two ordinary phones in a basic intercom.

Powerful Amplifier (CB18826E)
This powerful amplifier with 2N3055 transistors at the output provides a few tens of watts rms on a...
Night Switch (CB491)
This circuit turns on a lamp when the night comes and turn it off in the morning. The circuit...
Piezoelectric Transducer Amplifier (CB15928E)
This amplifier, suggested by National Semiconductor, is characterized by its very high input...