BA11-D Mounting Box
They were principally mounted in the H960 series of 19"-wide racks produced by DEC. Those provided 63" of vertical mounting space, divided into units of 10-1/2", which were further subdividable into a pair of 5-1/4" spaces. The 10-1/2" tall BA11-D mounting box was designed for these spaces, and could contain up to 5 standard size (4-slot) system units.
BA11-D's were principally used in 'basic box' roles, not as expansion boxes. The former contained the CPU, and had a front panel.
The BA11-D came with the H750 Power Supply; it was a separate unit, also mounted longitudinally in the box, at the right-hand side. It contained two transformers, a PCB which supplied +15V (1A) and -15V (8A), and some +5V (20A); an H744 +5V Regulator provided the balance (20A).
The power distribution panel (which contained the older 9-pin versions of the standard DEC power distribution connectors) was at the frontt. A BC05T (110V input) or BC05U (220V) line set controlled the main AC power.
The system units were mounted longitudinally, facing up; they were generally mounted with the A-row connectors at the back.
A pair of cooling fans was mounted at the front of the box, to provide air-flow to the boards; the power supply had its own internal fan, also at the front. It had a pair of connections to the standard DEC Remote Switching Control Bus, so it could turn other units off and on with its power switch
The BA11-D's dimensions were 10-1/2" high, 19" wide, and 23" deep.