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.
We found this active crossover in a Radio Electronics magazine from June 1961. Note the different...
Found in Popular Electronics from the 90s, this circuit serves to indicate the output level of a...
If you are on an old PC that you use for experiments, control or other applications, this circuit is...