This circuit is from the 80's, using an integrated of the time. The circuit serves as a reference, as this type of dialing is no longer used today.
This circuit found in a European publication from the 1980s, is based on PLL 566. The frequencies...
When the lights turns off this circuit will produce a sound like a cricket. When the lights are...
This circuit causes an LED to flash at a frequency determined by capacitor C1. The circuit can be...