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.
Suggested by an American documentation for 1969 neon lamps, this circuit provides SCR control with...
This circuit is designed to measure very weak currents, in the order of picoamperes. We found it...
The 709 integrated circuit is not common today. The circuit is from American technical...