DVR 522 User Guide available on Dish website

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522 DVR User Guide - click here
From the first page of Chapter 2, re: the "mode button":

Mode - Indicates if the receiver is in Single or Dual mode. This feature is
reserved for future use and your receiver should always be in Dual mode.

Pretty much what we already knew...

 

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At the above page is a link for "Stickers" that seemingly doesn't work.

Try that link and if it fails with a "page not found" error correct the spelling in the URL from "stikers.pdf" to "stickers.pdf" (note the missing letter "c") and you should be able to view the page.