DD11-B backplane
From Computer History Wiki
The DD11-B backplane is a 4-slot UNIBUS backplane system unit; it was normally installed in a BA11 mounting box. It used the early 9-pin DEC power distribution connectors.
The two hex-width slots were wired to support a DF11 Communications Line Adapter (in the A-B connectors) along with a quad-width serial line interface, such as the DL11 or the DU11.]
