Disclosed herein is a critical band encoding technology (CBET) system
having at least one portable people meter (PPM) and a home base station
and/or household hub, the CBET system containing a radio frequency (RF)
proximity detection and identification system, comprising at least one RF
transmitter for receiving a control signal, modulating an RF signal to a
present modulation frequency upon receipt of the control signal, and
wireless transmitting the modulated signal; and an RF receiver for
receiving the wirelessly transmitted modulated signal, determining the
modulation frequency, and transmitting the modulation frequency to a
remote location, wherein the transmission power of the RF transmitter is
preset to transmit the modulated data within a predetermined range.