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 circuit can measure frequencies up to just over 1 MHz and uses CMOS technology. The circuit is...
This variable oscillator was found in a Mullard transistors manual from 1960. The resistor R5 is...
This circuit, from a 1988 documentation, consists of an automatic temperature control using an NTC...