This circuit triggers an alarm in the event of a power failure. The circuit is from an 80's documentation, being powered by 9 V battery. The parts are common today.
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...