This 6-tube two-channel amplifier was found in an American documentation from 1947. The circuit is two-channel with a separation of bass and treble.
This elementary receiver with a crystal earphone was found in Japanese documentation from the...
This stable 20 MHz oscillator was suggested by the National Semiconductor's Linear Applications Handbook...
This circuit allows controlling a LASER pointer with an input logic signal. R has 10 ohm for 3 V...