Hi survtech,
Called Pelco today and yes they are very nice people to deal with.
Although they do not have detail info on the 22 pin connector on the DD5AC nor the back box for public use. They only service these units at their location. As you know some service manuals are almost impossible to locate. They did send me info on what back box units to use on the DD5AC.
I will use reverse engineering and trace the lines back from the plug to the PCB components. Being a electronic technician for 40 years, I may just find the function of the pins. The chase will be interesting.
Take Care,
stick2itkid