This circuit rejects frequencies around 1 kHz and can be adjusted using C1. Equivalent operational amplifiers can be used, and the power supply must be symmetrical.
This circuit was found in an American 1980s documentation. The components are current but most...
This simple timer for incandescent lamps or other non-electronic charges uses a triac as a control...
Found in a Radio Electronics store from the 90s, this circuit acts on the alternator. The circuit...