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.
This circuit adds a beep to turn on with car flashers that do not have this feature. A 47 ohm to...
Depending on the value of C1, this oscillator can produce signals of up to 1 MHz. For a capacitor of 10...
This commercial circuit, sold under the designation H531 in Japan in the 1960s, used three...