This interesting reflex receiver used a different component, which at the time was showing up. The receiver is from a 1924 documentation and used a sodion tube.
When the input of this circuit goes to high level, the LEDs start to flash alternately. The...
This circuit already uses an integrated circuit from the time. Note the different encapsulation of the...
This power charger was found in a 1990s issue of Popular Electronics. Integrated circuits must be...