I think that all devices that use 2.4 gigahertz are required by law to use collision avoidance technology. What that means is that they do not broadcast a signal until they find a clear channel to broadcast on. These radios do their own frequency control, that should include cell phones and other uses. The recievers only recognize the, oh I guess that "language" would be a good term for it, that its own transmitter uses to modulate the signal. If the reciever hears a signal but it is the wrong "language", it knows that it is not from the correct transmitter. The transmitter scans the radio traffic to find an unused frequency, then it broadcasts on that unused frequncy in a language that only its reciever recognizes. When you turn on your reciever, it scans the radio traffic until it finds a signal that is in a language that it understands and locks into that frequency. The Spectrum DX7 uses a different language for each different model in its memory, that way, if you are on the wrong model, nothing happens.

Exactly how it does it I have no idea. Black magic for all I know. But, so far my DX7 has worked flawlessly.