"Alexander Grigoriev" wrote in message
link.net...
Many cellphones have dictophone capability. How do you tell if the
cellphone in the visitor's pocket is not recording? The phone could be
also simply connected to another remote one, which would do the actual
recording.


Detecting and locating any device intentionally transmitting
an RF signal is trivial in relation to this discussion. But the
kind of device I have described can certainly detect that it
is responding to the audio pattern, and locate it.

Luck;
Ken