This adjustable frequency circuit was found in December 1986, Radio Electronics magazine. The base frequency is given by C1 and the power supply must be 5 V.
This circuit is from a Radio Electronics magazine from December 1971. The resistors are power...
This general purpose circuit was found in a Popular Electronics. It is intended for detecting the...
This circuit produces a tone by a small loudspeaker. Frequency depends on C1 and C2. These...