This medium power circuit is from an English publication from 1989. The integrated circuits are of types that are still obtainable. The power supply must source at least 2A.
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This circuit can be used to recognize a tone by its frequency. When this tone is present in a...
This circuit is from a 1975 amateur radio manual. The components can be approximated to the...
This circuit is from an English publication from 1976 but can be easily assembled with BC548...