This interesting circuit of an Electronic Design stores the highest voltage of two applied to its inputs. The circuit is from 1964 and can be adapted to use modern components.
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...