B21126E)
This circuit was taken from an old Popular Electronics. The circuit can have its frequency changed from an external signal. The center frequency is given by C1.
We found this circuit in a 1987 documentation, but it can still be easily assembled. Its output must...
This circuit that emits siren sound can be used in a fire alarm. We found it in an old American...
Found elsewhere in this section, this circuit is from the April 1971 Radio Electronics magazine. Note...