DM11 distribution panel

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The DM11 distribution panel (formally, the DM11-AA 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, and connected either to local terminals, or to modems.

M791 connector card

Both of these devices used a custom system unit backplane, containing multiple cards; one or more flat cables connected the device to the separate 5-1/4" high rack-mounted dual-height distribution panel, via a Berg connector on single-width M791 cards plugged into the panel's backplane.

Modular 'line conditioning' units were installed in the panel's backplane, 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), each card of which also supported only one line.
M5960 TTL to 20mA Level Converter
M594 TTL to EIA Level Converter
The DM11-DA included:
  • M596 - TTL to 20mA Level Converter
    • The M5960 was a later version of this card
  • 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)
  • BC01R cables (4 per M594, probably attached to an M957 or M970 card)

Note that these two were both DF11 cards; however, they were plugged into different slots in the DM11 distribution panel backplane from those used by cards used for single lines (below).

The DM11-DC consisted of four M594s and cables, plugged into individual line slots.

Board locations

There were two groups of separate slots at the ends of the distribution panel's backplane into which the 4-line cards plugged; a group of 16 slots in the middle could hold the DF11's or DM11-DC's.

M973 20mA Mate-N-Lok header card
M970 EIA Berg header card
Slot A B
1 M971 Line 00-15
2 M971 M971
3 M971 M974
4 Line 08-11 Line 00-03
5 Line 12-15 Line 04-07
6 Line 00 Control Line 00 Data
7 Line 01 Control Line 01 Data
8 Line 02 Control Line 02 Data
9 Line 03 Control Line 03 Data
10 Line 04 Control Line 04 Data
11 Line 05 Control Line 05 Data
12 Line 06 Control Line 06 Data
13 Line 07 Control Line 07 Data
14 Line 08 Control Line 08 Data
15 Line 09 Control Line 09 Data
16 Line 10 Control Line 10 Data
17 Line 11 Control Line 11 Data
18 Line 12 Control Line 12 Data
19 Line 13 Control Line 13 Data
20 Line 14 Control Line 14 Data
21 Line 15 Control Line 15 Data
22 Line 08-11 Line 00-03
23 Line 12-15 Line 04-07

The M974 was for diagnostics; it was removed for normal operation. For level conversion of the control leads, an M594 is used with the DM11-BB (says the documentation; the DM11-DC is probably meant); a W404-A with the DM11-DB; left empty with the DM11-DA. For the data leads, an M973 is used with the DM11-DA; an M970 with the DM11-DB or DM11-DC. In slots 4-5, an M594 is used with the DM11-DB; in slots 22-23, an M596 is used with the DM11-DA.

Further reading

  • DM11-BB Modem Control Option Engineering Drawings - not available online

External links