We found this circuit in the July 1994 Radio Electronics magazine. The circuit uses a general-purpose transistor, and the power supply can be up to 12 V depending on the relay.
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...