LM741 Voice Filter (CB25936E)

This 300 Hz to 3.4 kHz filter was found in the May 1989 Radio Electronics magazine. The circuit requires a symmetrical power supply.

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Headlight indicator 555 (CB9118E)
This circuit warns when the headlight bulb is on. We found it in a Popular Electronics from the...
Variable Active Cycle 4093 (CB15916E)
The oscillator shown in the figure keeps its frequency constant in an active cycle adjustment...
Two-Transistor MW Receiver (CB23975E)
This circuit was found in an Argentine publication from the 1970s. The circuit can be assembled with...