This circuit was found in the March 1984 issue of Radio Electronics magazine. The sensor is a transistor. The module is a common type at the time.
The four gates of a 40111 IC are used in thes two-out circuit. The output chages their state in a...
This low power, low voltage circuit was found in old General Electric documentation. Transistors may...
This grounding test circuit was found in an American 80's documentation. The circuit is for the...