Found in an American documentation from 1969, this astounding circuitry makes a relay operate on 3 Hz cycles. The relay is of the high voltage type of the time.
This circuit was found in an old documentation and can be implemented with BC549 transistors. The...
This mid-waveband receiver was found in a book on transistors from 1954. The antenna coil is of...
Old multimeters used a 22.5 V battery for high resistance measurements. If you have one, you...