Found in a 1980s American documentation, this circuit operates with 5 V signals requiring 55 cycles of 500 Hz for tone recognition. The circuit can be adapted to operate with other frequencies.
Other operational amplifiers series, such as the MC34072, MC34074, MC35071, MC35072, MC35074 d...
This symmetrical power supply with a current of the order of 100 mA was found in an old...
This circuit for semiconductor laser excitation and modulation was found in an American...