This filter is from a 1977 publication. The circuit employs three 741 or other operational amplifiers. The supply must be symmetrical and the components with (*) are low tolerance.
This circuit is like the previous one except that it can be triggered electronically. The circuit is...
Found in 90s Radio Electronics, this audio indicator makes use of an integrated circuit that is...
Found in the October 1992 Radio Electronics magazine, this oscillator is controlled by switch S1....