DF11 Communications Line Adapter

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M594 DF11-A TTL to EIA Level Converter

The DF11 Communications Line Adapter performs two functions for serial line communication interfaces on PDP-11 computers: i) converts from TTL signal levels to the voltages, etc needed by a given serial line standard, and ii) produces the physical connector needed for that standard.

M970 EIA Berg header card

A DF11 usually involves two single-width cards, one holding the circuitry needed, and the other providing, sometimes with a cable plugged into a Berg connector, the interface connector. At least one dual-width adapter (the DF11-B) existed, though.

M5960 TTL to 20mA Level Converter

The DF11 plugs into a common backplane with the serial interface. DF11's are used with DP11, DM11, DH11, DC11; and DL11 and DU11 UNIBUS serial interfaces (the latter two only in DD11-B backplanes, where the DF11 plugs into the A-B connectors). They may also be used in some versions of the PDP-11/05 or PDP-11/10.

M973 20mA Mate-N-Lok header card

DF11 models include:

  • DF11-A (M594, M957-BC01R, M970-BC01R for modem cable) - EIA RS-232 adapter
  • DF11-BA (M586) - integral modem for connection to a telephone line
  • DF11-BB (M587) - integral answer-only modem
  • DF11-F (M596, M973) - 20m current loop adapter; 'active' mode (up to 300 baud)
  • DF11-G (M595, BC01T-BC01Y) - custom 20mA interface to a Bell 301/303 modem
  • DF11-K (M598, M973) - 4-wire opto-isolated 20mA adapter; 'passive' mode (up to 2400 baud)

The M5960 is a later, apparently improved 'active' 20mA interface which replaces the M596. The M598 (DF11-K) has jumpers to allow each channel to be changed to 'active' mode.

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