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 1000: 1 voltage-controlled filter circuit was found in an Electronics Today International in a 1980s...
Found in a 90s Electronic Design, this circuit provides a highly stable 60 Hz sine signal for...
This one-digit photometer using CMOS circuits was found in a 1989 documentation. The circuit is...