Phone circuit (CB8709E)

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

Electronic Bingo (CB17441E)
This 2001 CMOS digital circuit draws numbers from 00 to 99 and can be expanded. However, it does...
10 W amplifier TDA2006 2 (CB15243E)
This amplifier makes use of a simple 12 to 30 W source, having been found in the SGS manual of...
Oscillator MM74C04 (CB14254E)
The circuit shown is from the Linear Applications Handbook and the maximum frequency is in the...