This analog tachometer was found in Radio Electronics from the 90s. The components used can still be found with some ease.
This RF circuit measures transmission power from 0.25 W to 10 W. The maximum frequency depends on...
This General Electric circuit was published in 1970. The LED is infrared and the voltage according...
Found in a 1968 Motorola publication, this circuit generates a high-powered audio tone when...