This FM receiver tuning step circuit was found in a 1960 documentation. No information about the coils is given, but the FI used at the time was 10.8 MHz.
This circuit generates sinusoidal signals between 300 and 3000 Hz. We find a 303 Circuits from the 90's....
This amplifier for audio transmission lines was found in a 1961 American publication. The critical...
Old phones with dials can be used in a simple home intercom system, as this circuit from Popular...