In the case I mentioned the cell phone was just on standby and the radio was a new Airtronics 4 channel radio. Before I asked the guy with the cell phone to switch it off I did have him back up a few feet first and the servos stopped twitching. The problem was when the cellphone was within about 3-5 feet. If the power goes up when the phone is about to ring, this will probably compound the problem. The phone obviously doesn't have to be on the same frequency to cause interference. It may a 4th or 5th harmonic causing the problem or the phone may just be putting out more power than the recevier can filter out but from my personal experience its something to be concerned with.[8D]