This circuit is from an American documentation from 1975. The circuit uses components of the time which can be replaced by modern equivalents. The coupler is homemade with a lamp and a photocell.
This circuit with the integrated uA739C was widely used in Japanese amplifiers for cassette...
We have here a very interesting project found in a 1982 publication. By the operation of the...
This sixty Japanese commercial radio used 6 transistors in a superheterodyne configuration for...