BA11-L mounting box

The BA11-L mounting box was for many years a standard hex system unit backplane mounting box for the H960 series of 19"-wide racks produced by DEC, one of the BA11 mounting boxes.

The H960 racks 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 5-1/4" tall BA11-L mounting box was designed for these spaces, and could contain up to 2 standard size (4-slot) system units.

BA11-L's were used in both 'basic box' and 'expansion box' roles. The latter was used to hold extra devices, and had a blank front panel. The former contained the CPU, and had a front panel of some sort - either a programmer's console, or an operator's console.

In the PDP-11/04 (the model which used this mounting box to hold the CPU, although the PDP-11/34 was occasionally seen in one) the front panels were the KY11-LA Operator's Console and the KY11-LB Programmer's Console (the same for both CPU's).

The system units were mounted longitudinally, facing sideways; they were generally mounted with the A-row connectors at the back, next to the power distribution panel.

The BA11-L came with the H777 power supply, which came in several versions, with different mixes of voltages supplied. The supply was a separate unit, also mounted longitudinally in the box, at the side. A single cooling fan was mounted at the front of the box, to provide air-flow to the boards; the power supply had its own internal fan, at the front.

The BA11-L's dimensions were 5-1/4" high, 19" wide, and 25" deep; it weighed 45 lbs (without the backplanes or boards).