The base unit transmits signals across an unused FM frequency, and the user can select from numerous radio stations with the tuner, which also has a "Tell Me More" button that can be used to obtain more information about songs being broadcast, or even to purchase MP3 files or CDs.

CNN: Sonicbox brings Net radio into your living room

As more customers sign up, service providers simply add more base-stations because all can use the same frequency without causing interference.

ECONOMIST: MONITOR

The concerns stem from the emissions of radio frequency (RF) radiation by both the handsets and the base stations that transmit and receive the signals.

BBC: Public Petitions Committee