This shield circuit is from an American documentation from 1969. The components can be modified according to the relay and power, and the coupler can be of a modern type.
Intended for use with signals from tape recorder pickups, this circuit was found in the December 1972...
In the figure we have the configuration of a voltage regulator with 3 transistors. The components depend...
This circuit was found in an 80s documentation. The integrated circuit used is from that time,...