In the figure we have one of the many options found in this section for an intercom using ordinary phones not in use. This was obtained in a Popular Electronics from the 90s.
The simple touch of the fingers on a sensor causes this circuit to drive a motor that goes into...
This simple circuit found in an American 80's documentation simply blames if there are toxic gases in...
This circuit is from Motorola's 1990 Linear Databook. The transistors allow equivalents and the...