Found on a 1969 EDN this circuit switches a current from a digital control signal. The impedance of the circuit ON is approximately 10 ohms. Modern equivalent transistors may be used.
In the figure we have an amplifier configuration found in an 80's documentation. The power supply is...
Suggested by a Philips documentation from 1970, this circuit uses period components, operating at 50...
This circuit was found in a Radio Electronics from April 1990. The circuit has 5 equalization...