This circuit was found in an American documentation from 1970. We can increase the number of multiplier steps to have higher output voltage. The operating frequency is around 1.35 kHz.
Found in a Hands-On Electronics from the 90s, this circuit produces the dial tones of an old...
Found in Radio Electronics from the 90s, this circuit has several outputs with different pulse...
This circuit, found in 2002 documentation, triggers LEDs when a phone call is received. The LEDs...