This simple bridge circuit can be used for impedance or resistance measurement using a high impedance earphone as an indicator. The circuit is from an American 80's documentation.
Using a 4017 as a base, this circuit from a 1990s Popular Electronics generates low-frequency...
This diagram from a 1967 documentation shows how to switch high voltage neon lamps with 5V TTL...
This circuit was found in a 90s EDN. It activates a protection relay in case of reversing the...