Adjustable reference (CB21540E)

We found this circuit with 5.3V zener in a Philips publication from the 60s. The op amp could be a modern equivalent.

Audio crossover filter (CB23743E)
We found this active crossover in a Radio Electronics magazine from June 1961. Note the different...
Output indicator 555 (CB20967E)
Found in Popular Electronics from the 90s, this circuit serves to indicate the output level of a...
Serial Driver RS232S (CB17022E)
If you are on an old PC that you use for experiments, control or other applications, this circuit is...