freq. change
There have been several radio systems with "Synthesized" frequency modules, which are able to be tuned to any of several frequencies (sometimes all R/C frequencies on 72 mhz band...). I don't remember the name of Futaba's module with that ability. HiTech's Spectra module systems have the ability to change frequencies without changing modules or crystals. There's also a system with a RX that "actively seeks" the TX frequency, and there's a TX supposed to be hitting the market with a built-in frequency scanner, to help you choose an unused frequency with it's synthisizer. (there's a flaw in there... doesn't prevent someone from turning on another TX...AFTER you chose that frquency.)