This circuit is from a Radio Electronics from March 1970. The integrated circuit used is one of the first for this purpose, being improved later leading to types that succeeded it.
Found in English documentation from the 1980s, this circuit can use any germanium diode. The...
This configuration, which requires a symmetrical power supply for the 741, can be implemented with other...
This 3-digit code switch was obtained from an old American documentation. The capacitor is 470 uF...