Try the phrase "cell phone detector schematic" in a search engine. The third hit from Google was this: http://physics.indiana.edu/~ptsmith/cell/
Try the phrase "cell phone detector schematic" in a search engine. The third hit from Google was this: http://physics.indiana.edu/~ptsmith/cell/
This is the audio output. Either the sound will come from the speaker, if no plug is in the jack, or the sound will come from the headphones or other appliance if there is a plug in the jack.
From the website: "Headphones, a more powerful amplifier, or a computer's audio input can also be plugged into the phone jack."