Dark activated switch with hysteresis (CB7871E)

Found in a 90s American documentation, this circuit can be used as a shield, just change the coupler for one that uses a phototransistor.

| Clique na imagem para ampliar |

Decade Counter with Nixie Tube (CB20141E)
This is an old test circuit for integrated TTL counters, feeding a Nixie tube, common at the time....
Water Level Alarm (CB12215E)
I found this circuit in an Electronics Handbook from 1989. The circuit can be assembled with a...
Audio Booster (CB22489E)
This circuit makes use of a 2N301 germanium power transistor. We found it in a documentation from...