Signals encoded with watermark information are generated and broadcast
into a protected area for capture by illicit recording devices along with
their intended targets. An illicit recording in which at least a portion
of the broadcast watermark signals are recorded is obtained and
correlated with a known position of the broadcast watermark signals to
yield the location of illicit recording devices. In an alternate
embodiment, a surveillance device, being image and time synchronized with
a signal broadcasting device, monitors and records the protected area.
Illicit recordings containing the broadcast watermark are obtained and
correlated with corresponding recordings taken by the surveillance device
to identify the location of illicit recording devices. In an alternate
embodiment, the surveillance device further monitors the quality of the
broadcast watermark signals and adjusts them accordingly to achieve a
desired quality level.