Standard 1 MHz Oscillator (CB9653E)

We found this circuit in an old American documentation. Transistors can be modern equivalents.

Telegraph Practice Oscillator (CB6474E)
Found in a 1965 Radio Shack documentation this oscillator can be used with modern general purpose...
Voltage Frequency Converter with the 4047 (CB12736E)
In the figure we have a voltage / frequency converter circuit that can be used as a transducer interface...
Headphone Amplifier LM3900 (CB13929E)
This small stereo amplifier for headphones was found in a documentation on integrated circuits from...