We found this circuit in a Radio Electronics magazine from November 1976. The clock frequency is divided by 10 and the maximum value depends on the integrated circuits used.
This circuit reinforces signals in a frequency range between 1500 and 2000 Hz for use in...
When a small air current reaches the piezoelectric sensor, a small audio signal is generated and...
This circuit is from a Poptronics, American magazine from August 2000. The circuit can be...