It serves as a reference, since today we can have simpler and more compact solutions. This circuit is from an Electronics Experimenter Handbook from 1992. The integrated circuits are from that time.
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...