DM11 distribution panel

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.

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

Modular 'line conditioning' units were installed in the distribution 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

M594 TTL to EIA Level Converter

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.

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, probably attached to an M957 or M970 card)

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

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