9V power source (CB21164E)

This simple circuit with a 5V regulator was found in an American documentation from the 90's. The output voltage is adjusted in a trimpot.

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RC Oscillator (CB5993E)
In this oscillator circuit using 3 TTL inverters we have all the conditions for the frequency...
Tone control (CB12811E)
We obtained this circuit from an old Argentine magazine. The circuit originally uses germanium...
Digital Frequency Detector (CB13288E)
This TTL digital circuit from Texas Instruments documentation from the 1970s used the company's SN types...