Active audio filter (CB21770E)

This circuit was found in a 1977 documentation for radio amateurs. Integrated circuits are common operational amplifiers.

12 V Stabilizer (CB8803E)
Found in General Electric's 1966 documentation, this circuit uses company reference diodes, which are...
Sound Indicator (CB16613E)
We found this simple warning circuit for car blinkers (arrow) in a 1987 publication. The relay must...
Touch on and off switch (CB9376E)
Found in RCA documentation from the 90s, this circuit uses integrated components from the time. The...