With this system you can disconnect phone lines in case of need for protection. The circuit is from a 1989 documentation working only with analog lines.
This circuit was found in an American documentation from the 60's. The transistors are from the...
This oscillator is indicated for the adjustment of FI of FM radios, having its frequency...
This configuration triggers an external circuit or simply an LED for time given by R1 and C1 (T =...