We found this circuit in the Encyclopedia of Electronic Circuits Volume 5 from 1995. It uses a 3-terminal transducer from the time. The circuit is triggered by light.
This circuit is a driver for R-2R network of AD converters. We found it in manufacturer...
This circuit was found in an American publication from the 60's. The transistor is made of...
This circuit produces an audio tone on the speaker or magnetic capsule. Rx must be such that added...