Phone circuit (CB8709E)

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

Relay with latching (CB23664E)
The figure shows how to obtain a locking relay for an alarm circuit with sensors in series and in...
Neon flashlight (CB21737E)
Found in Popular Electronics from 1969, this circuit uses a neon lamp from the time that had...
DC Motor Speed Control (CB17401E)
This is a simple rheostat circuit for motor control that works with voltages from 6 to 12 V. The...