This is an interesting configuration of the LM317 voltage regulator found in an EDN from the 90s. The circuit uses an optical coupler and is intended to supply constant current to a sensor resistor.
This fast converter using operational was found in a 70s American documentation. The circuit can be...
This circuit uses two sensors that are placed at the intersection of a miniature railroad, causing the LED...
This RF wattmeter was found in an American 1980s documentation. The components are common and the...