This very complex circuit in terms of the number of transistors was found in Radio Electronics from March 1966. The circuit is for low impedance headphones. The transistors are from the time.
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...