This circuit was found in a 80s American documentation. The zener diodes determine the points of action of each stage and the transistors can be general purpose types.
This shield circuit allows recording of the signal from a serial output on a cassette recorder, with...
This Japanese radio receiver is from the 60s. It has 6 transistors and is powered by 4 batteries with...
The integrated circuit used is a voltage reference from Motorola. This configuration was obtained in...