This 1974 circuit uses two 555 integrated circuits in a very traditional configuration. The circuit can be powered by voltages from 9 to 12 V and for greater volume an amplifier stage can be added.
ON Semiconductor MC74VHX1Gx Logic ICs The Mouser Electronics series 74 Logic ICs are available for...
Found in a 1980s German publication, this circuit tests batteries by type. The circuit is based on a...
This 300 kHz and 400 kHz two-channel transmitter for TV remote control appeared at Radio...