This circuit lets through the 300 Hz to 3kHz range that corresponds to the human voice. We found it in the Radio Electronics magazine of February 1990. The circuit uses both parts of the LM381.
Found in an old neon lamp applications manual, this circuit directly triggers an SCR. R and C...
This 20 MHz bandwidth circuit was suggested by the National Semiconductor in 1970 documentation. Modern...
This circuit cuts out ads between songs, based on the fact that the speech signal has small...