BA40A Expansion Adapter
From Computer History Wiki
The BA40A Expansion Adapter is an optional attachment for the MicroVAX 2000/VAXstation 2000 system unit that permits communication between the expansion box and the system unit.
The Expansion Adapter contains two connectors: A and B. Those letters are stamped on the Expansion Adapter to identify the connectors. A is the connector for an expansion box containing a tape drive. B is the connector for an expansion box containing a fixed disk drive. A third opening is covered by a metal plate and is not used by the MicroVAX 2000/VAXstation 2000.
The Expansion Adapter is connected to the MicroVAX 2000/VAXstation 2000 system unit by a flat cable.