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 Popular Electronics. Its purpose is to warn the visually impaired when a glass...
This circuit was obtained from a Popular Electronics from January 1967. It has a...
This ultrasonic transmitter was found in a 1974 documentation. The receiver is the CIR11753 or...