DM11-BA Modem Control Multiplexor

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The DM11-BA Modem Control Multiplexor allows asynchronous serial lines connected to a UNIBUS device controller to be connected to modems. It could be set to interrupt the CPU when a modem control line (Ring, Carrier, etc) changed state. It is a re-implementation of the DM11-BB Modem Control Option; instead of plugging into a controller backplane like the -BB, the -BA plugs into a standard UNIBUS MUD slot.

It is program compatible with the DM11-BB (although a single DM11-BA only supports 8 lines, unlike the DM11-BB, which handled 16), and is implemented as a single hex board, the M8640.

H317-B with cover off

It connects, using two flat cables plugged into Berg headers on the board, to a passive distribution panel; either one usable with the DM11-BB (such as the H317-B), or the newer H317-M or the functionally identical H317-P (the latter has improved EMI shielding).