Apple AirPort Extreme 802.11n (4th Generation) - Manual (Page 32)

32 Chapter 4 Tips and Troubleshooting
 Certain electrical devices such as power lines, electrical railroad tracks, and power
stations
 Cordless telephones that operate in the 2.4 or 5 GHz range. If you have problems
with your phone or AirPort communication, change the channel your base station or
AirPort Extreme uses, or change the channel your phone uses.
 Nearby base stations using adjacent channels. For example, if base station A is set to
channel 1, base station B should be set to channel 6 or 11.