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.
In the figure we have the way to use the transistors of an old-paired pair as a trigger circuit. The...
We found this synchrodyne receiver for the medium or short-wave band in the Radio Electronics...
This old circuit, from a 1992 documentation, was used with tape recorders acting as playback. The...