We found this circuit in the December 1998 issue of Electronics Now magazine. RF transistors such as the BF494 or BF495 can be used. The circuit works at lower frequencies.
This sensitive passage alarm was found in the August 1971 Radio Electronics magazine. The light...
This filter has the components calculated for the frequency of 1 kHz but can be changed. The input...
The direction of rotation of the M motor can be controlled by an Arduino or another...