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.
This complementary-output amplifier can be used to source a good qualuty signal to high impedance...
This circuit can be adjusted between 0.2 and 2 V to trigger with chosen voltages comparing them with...
Although it is a common configuration today, this circuit was taken from an old publication. The...