Allied Telesis AT-WA7400/EU - Manual (Page 100)

Chapter 9: Configuring the Wireless Settings
100
The channel defines the portion of the radio spectrum the radio uses
for transmitting and receiving. Each mode offers a number of
channels, dependent on how the spectrum is licensed by national and
transnational authorities such as the Federal Communications
Commission (FCC) or the International Telecommunication Union
(ITU-R).
The default is Auto, which picks the least busy channel at startup time.
3. Click Update to save your settings