This circuit monitors an old-style analog telephone line. We found it in the September 1991 issue of Radio Electronics magazine.
This digital CMOS circuit generates sinusoidal signals from a 10 kHz rectangular signal. The...
Found in an 80's Elektor, this circuit can use any equivalent optical coupler. The buzzer is of the...
Found in a 1965 Electronic Design, this circuit limits surges in a load when power is applied. The...