From Computer History Wiki
The DD11-D backplane is a 9-slot MUD backplane system unit. It was normally installed in a BA11 mounting box.
There are two versions, the DD11-DF and DD11-CK, intended for use in the BA11-F Mounting Box and BA11-K mounting box, respectively; they differ basically only in the length of the power harness, although the two provide +5VB (battery backup) on different pins of the DEC power distribution connectors. A DD11-DP existed as well, for use in the BA11-P card cage.
- DD11-D Engineering Drawings - DD11-DK and DD11-DF wiring harness requirements can be found on pages 6 & 7