This is an old test circuit for integrated TTL counters, feeding a Nixie tube, common at the time. The circuit is from the 90's, not being given the power supply.
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...