DM11-BA Modem Control Multiplexor
From Computer History Wiki
The DM11-BA Modem Control Multiplexor is a re-implementation of the DM11-BB Modem Control Option; instead of plugging into a asynchronous serial line device controller backplane like the -BB, the -BA plugs into a standard UNIBUS MUD slot. It is implemented as a single hex card, the M8640.
It connects to a passive distribution panel, either the H317-M or the functionally identical H317-P; the latter has improved EMI shielding.