So it can tell semiconductor junctions of an MP3 recorder from semiconductor
junctions of non-recording devices?

Th OP question was detection not *any* semiconductor device, but a MP3
recorder. By the way, the recorder doesn't have to be in that room. Enough
to have a connected cellphone in a pocket.


"Dana" wrote in message
...


Yeah, so what. There are devices that can detect semiconducter junctions.
MP3 players have semiconductor junctions, hence they can be detected.


Now how about the phones that can record?

They also have semiconductor junctions, hence they can also be detected.