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 circuit was found in the ON Semiconductor's Thyristor manual of the 1980s. The high quality...
This simple injector circuit can actually be powered by voltages from 3 to 9 V. The frequency is...
This 10 kHz filter is based on a 741 operational amplifier. The circuit is from Electronics Now...