Found in a Raytheon transistor manual from the 1950s, this circuit uses one of the first commercially available transistors, the CK722. The circuit is for using a small speaker as a microphone.
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...