This circuit was obtained from the February 1992 Radio Electronics magazine. In it, a bar of 4 LEDs flashes continuously at a speed given by C1 and the setting of R3.
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...