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.
This circuit is from a 1965 General Electric Hobby manual. The circuit uses only passive...
We found this circuit in a 1967 RCA SCR manual. The circuit uses components from the era. The...
Found in American documentation from the 1970s, this circuit can be designed based on a modern SCR,...