This circuit was found in a 90s Popular Electronics. It produces a muted tone similar to that produced by a bell. The signal must be applied to an amplifier.
This circuit for RF signals was found in the March 1987 issue of Radio Electronics magazine. The...
We found this circuit in Texas Instruments' Linear Circuits Applications. It is a low consumption peak...
This medium wave radio must use a high impedance piezoelectric, crystal or magnetic phone and the...