This circuit allows you to simulate an analog telephone line for the repair and testing of devices. The circuit is from 1994 and all the components used are common.
This transistor gain meter was found in a 1960 Sylvania transistor manual. The circuit is for...
This circuit for monitoring telegraphy transmissions was found in a 1975 CQ magazine. Transistors may be...
This is the version of the previous circuit with shadow activation. The circuit can use relays from...