This sophisticated filter for audio signals was found in Radio Electronics magazine. The frequencies are determined by LC circuits. The circuit has selectivity selected by a switch.
The circuit shown in the figure has elements for maximum gain at maximum speed. By setting the...
This instrument, based on a 555, measures frequencies up to 1 kHz, but its scale can be modified by...
Using a CA3130 operational amplifier, this circuit was found in an English publication from 1977....