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.
Found in a 1964 Electronic Design, this circuit must use transistors according to the supplied...
This oscillator that operates at 80 kHz was found in the July 1993 issue of Electronics Now...
This circuit was obtained from a 1967 General Electric manual. The circuit uses components of the time,...