This tone recognizer circuit that relies on R5 and C1 was found in the December 1994 issue of Electronics Now. The circuit operates on voltages from 6 to 12 V typically.
This circuit causes strings of lamps to flash alternately. The circuit can be changed to use LEDs....
This 80's General Electric circuit is guarded by the noise-guard for operating current. The...
This circuit is from a 1967 documentation. It consists of a sensor for memories used at the time....