This circuit, found in 2002 documentation, triggers LEDs when a phone call is received. The LEDs will flash alternately in these conditions. Common LEDs are used in this circuit.
This adjustable oscillator has the traditional configuration already presented in other articles. The...
This circuit appears in other versions on this site. obtained from other publications. This is...
This circuit decodes a 1800 Hz tone used in communications. The circuit is from an American...