This circuit is from a Mallory 1968’s documentation. The integrated circuit is of the time and the transistor admits equivalents.
This FM advertising suppressor (SCA) decoder circuit was suggested by Signetics in a 1980s...
We found this circuit in an old General Electric documentation. In fact, PUTs are not common...
We find this simple musical instrument in a 1977 Radio Shack documentation. The key resistors must be...