MCI 102C speedometer and cruise control questions

[Lomaric]

New to the forum, and figured there might be someone out there to assist me.  I have a 1989 MCI 102C with DDECII and ATEC, I have been trying to trouble shoot a speedometer and  cruise control not working issue.  The speedometer is a Dixson model.  My questions are:

1. Does the speedometer feed information into DDEC? 
2. Is the cruise control ring sensor the same as the speedometer sensor?
3. Is the sensor located on the front drum area or is in the back (possibly transmission)?
4. Is there a test that I can do to the speedometer to ensure it is operating (electrically)?

Thanks for your assistance.  I have a manual for the bus, but I am struggling with how the logic works and the location of the components.

Aaron