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 can be used both as a beat oscillator and for testing and adjusting AM receivers for...
Using a 4046 PLL, which is not very common nowadays, this circuit was found in the October 1994...
Found in a 1991 Hobbyst Handbook, this circuit monitors both battery and alternator voltage. The set...