This sensitive 5-band circuit was found in a September 1995 issue of Electronics Now magazine. The headphones, for greater sensitivity, should be high impedance.
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...