This circuit was found in a 1966 EEE. The circuit uses transistors from the time but can be made with modern equivalents. The operating frequency ranges from 0.1 to 1 kHz.
This circuit is based on operational ones found in documentation from the 90s. The frequency with...
This filter has a quality factor (Q) equal to 5 and uses the Texas Instruments TLC271 integrated...
This circuit recognizes a tone determined by the tuned input circuit (R3 / R4 / C2). The circuit...