Originally Posted by pdhenry
Unless I'm mistaken a GSM phone will also cause this interference as it periodically renews its connection to the tower, whether it's in use or not. My T-mobile phone used to excite my answering machine like that from time to time even if I wasn't getting a call or anything.
Not sure about GSM (no Cingular GSM in this area), but Cingular digital phones do this as well. When my phone (a Nokia 6030) is anywhere near computer speakers or an FM radio it causes the above descrbed interference. I get this interference a lot in my car as well.
On a related note, my company (one of the large package delivery companies) uses hand-held computers which communicate via cell technology. I can always tell when a unit is transmitting because I can hear that telltale "morse code" coming through the delivery truck's comm radio.