This 4-tube counter was found in Radio Electronics magazine from December 1959. The circuit uses a coil as a sensor to detect the passage of metallic parts or magnets.
The circuit shown was found in an American documentation from 1964. The circuit uses transistors of...
We found this antenna amplifier or Booster circuit in an Electronics Now from the 90s. The circuit...
This dimmer with a unijunction transistor and SCR appeared in Radio Electronics magazine in March...