This simple circuit to monitor the frequency of the power grid uses an analog indicator. The adjustment trimpot can be 4k7 and the indicator is 100 mA full scale.
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...