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 circuit uses an old National Semiconductor operational amplifier, but it can be implemented with...
In this circuit the regulation is made from a circuit in the LED cathode. The configuration is...
For the component values used in thisf this circuit, the frequency can be adjusted between 740 Hz and...