We found this circuit in a 1976 publication. The transistors can be BC547 or 2N2222. Crystals up to a few tens of Megahertz can be tested. The LED can be of any type. The capacitors must all be ceramic.
This simple neon lamp power indicator circuit was found in the January 1971 Radio Electronics...
This circuit was found in Radio Electronics magazine from June 1958. The maximum distance depends on...
Using two common operationals, such as 741, this circuit serves as a medium control in an...