DM11 distribution panel

The DM11 distribution panel was used with the DM11, and early models of the DH11 interfaces, to connect these interfaces to asynchronous serial lines which used a number of different low-level electrical interface specifications, either to local terminals, or to modems.

Both of these devices used a custom system unit backplane, containing multiple cards; one or more flat cables connected this to the separate 5-1/4" high rack-mounted dual-height distribution panel backplane.

Modular 'line conditioning' units were installed in the distribution panel to allow support of either 20mA serial lines (local only), or EIA RS-232 serial lines (local or modems - modems usually required a DM11-BB Modem Control Option as well as the basic asynchronous serial line interface).

Line conditioning

Three broad choice were available for line conditioning:

• Use any unit from the DF11 Communications Line Adapter series, each of which only supported a single line.
• Use the DM11-DA (20mA line conditioning) or DM11-DB (EIA, no modem control), each of which supported four lines; thus, with these, line conditioning could be mixed in groups of four.
• Use the DM11-DC (EIA, modem control), which also supported only one line.

The DM11-DA included:

• M596 - TTL to 20mA Level Converter
• M973 - Mate-N-Lok header (4 per M596)

and in the DM11-DB:

• M594 - TTL to EIA Level Converter
• W404 - DTR Jumper card (4 per M594)

Note that these are all DF11 cards; however, they were plugged into different slots in the DM11 distribution panel backplane from cards used for single lines.

The DM11-DC used only the M594, plugged into individual line slots.