Applying an operational of the time, this circuit of an old documentation can be elaborated with modern operational. The feed must be symmetrical.
This circuit triggers a remote doorbell when the phone rings. The circuit is for the 110 V mains...
This circuit uses na Unijunction Transistor (UJT) to produce a modulation tone for several...
This circuit was found in a Popular Electronics from April 1993. It is a voltage regulator circuit...