Sony RM-VL900T Operating Instructions Manual page 47

If none of the above have solved your problems, try the following before contacting
any Customer Support.
To reset the Commander to its factory settings
While holding 1 pressed, press t and 2 – until the
Commander reacts as follows.
The S (set) indicator and all Component Select buttons light up.
Then the Component buttons turn off one by one, followed by the S
(set) indicator.
When all have turned off, all settings are cleared, and the Commander
returns to its original state (including the preset series of functions on
SYSTEM CONTROL 1 and 3).
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