VIEWSONIC VS12276-1G - Manual (Page 19)

ViewSonic N2690w 17
(7) AFC：can be set to On or Off. If set to On, the TV will automatically detect TV
signals, and automatically adjust to the correct position in a certain frequency
range when the signal offset occurs.。
(8) Save: Save each setting for manual tuning.。
3. Channel list: Press the Left/Right button to enter the submenu; see the figure below.
You can edit the channel list according to the instructions at the bottom of the menu.