This circuit provides a signal when dialing occurs. The circuit is powered by the telephone line voltage itself. We found it in an old documentation.
This circuit was found in an American publication from the 50's. The transistors are made of...
The circuit shown is an amplifier for medium impedance headphones including bass and treble...
This circuit for an optical audio link using LED or LASER was found in a 90s QST magazine. The circuit...