US Patent 8631427 Audience detection

A technique is disclosed for identifying members of an audience tuned to a program broadcast by a programming signal source, comprising the steps of storing personal identification signals in a plurality of portable devices to be carried by members of the audience; periodically transmitting said identification signals from the portable devices; providing a stationary detector to detect the identification signals if they exceed a selectable response of said detector; and setting the selectable response of said detector to a level such that the identification signals are detected only if the respective portable devices are located relative to the detector in positions where persons can perceive performance of the broadcast program.