Phone circuit (CB8709E)

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

Pulse generator (CB8913E)
Indicated for applications in the analysis of logic circuits, this circuit was found in 90s Radio...
Automotive Voltage Regulator (CB1442E )
This circuit is from 1977 documentation, and high current equivalent transistor must be used. The...
Bipolar Pulse Counter (CB6616E)
Found in an Electronic Design, this circuit makes use of general-purpose bipolar transistors. The circuit...