This circuit doubles the frequency of an audio signal, thus changing its timbre. The circuit was found in an Elektor from the 90s. The components are common today.
This metering bridge circuit uses one power supply only. The operational ones depend on the...
This circuit is from the 80's, using an integrated of the time. The circuit serves as a reference,...
This 1967 Raytheon circuit uses an optical coupler of the era and has a range of 800 to 200 Hz....