This circuit is from a Radio Electronics from February 1966. The circuit is of a type that was found in many applications at the time as output from radios, televisions and other equipment.
This circuit from a Popular Electronics shows how to take the audio signal from a telephone line...
The coil of this transmitter has 4 coils of wire 26 or 28 in the form of 1 cm without core and on it...
In the figure we have another configuration of filter that uses the four Norton amplifiers of the...