This 300 Hz to 3.4 kHz filter was found in the May 1989 Radio Electronics magazine. The circuit requires a symmetrical power supply.
The automatic modulated siren circuit shown in the figure really produces an interesting sound...
This circuit for incandescent lamps was found in a 70s documentation. The circuit uses an SCR...
In the figure we have a circuit in which two moving bar/dot indicators are connected together to...