This 1980s circuit was found in Motorola documentation. The circuit uses period components that admit of equivalents. Light feedback in a modern version can be done by optical fiber.
This circuit was found in an American publication from 1968. The transistors are from the time,...
The components of this circuit are exchanged for modern equivalent such as 470 K for the pot and...
This circuits shows how to use in operational amplifier as a basic voltmeter. Power supply must be...