Asynchronous Serial Communications Programmer's Reference Manual (32022-90052)

Chapter 1 27
Introduction
Datacommunications and Terminal Subsystem (DTS)
If used for direct connections and remote modem connections only, each
HP 2345B DTC (DTC 48) can provide connections for up to 48 directly
connected devices, 36 remote devices using modems, or a combination of
both.
For HP 2345B DTCs, up to three of the DTC’s slots can contain a
DTC/X.25 Network Access Card. This card provides access to X.25
networks, and can be used to connect asynchronous devices through
PAD connections. Alternatively, a single Telnet Access Card per DTC
can be used to access MPE/iX systems from ARPA systems.
Each HP 2345B DTC provides six slots, each of which can contain one of
the following connector cards:
• Eight 3-pin RS-232-C local connections.
• Eight 5-pin RS-422 local connections.
• Six 25-pin RS-232-C modem connections.
• DTC/X.25 Network Access card (up to three per DTC, slots 1 through
5 only).
• Telnet Access Card (only 1 per DTC, slots 1 through 5 only).
Each HP J2070A (DTC 72MX) can provide connections for up to 72 local
and modem devices, if used for direct and remote modem connections
only. It provides four slots, with one slot used for the LAN card, and
three slots each of which can contain one of the following cards:
• Asynchronous processor board with three 62-pin connectors, for a
total of 24 RS-232 local or modem connections.
• Asynchronous processor board with three 62-pin connectors, for a
total of 24 RS-423A local connections.
• DTC/X.25 Network Access card (up to three per DTC).
• Telnet Access Card (only 1 per DTC).
The DTC 16 contains three slots. The first two slots and only the first
two slots (card #0 and card #1) can contain direct connect or modem
cards. The third slot (card #2) can contain only a DTC/X.25 Network
Access Card.
Each DTC 16iX and DTC 16MX can provide RS-232 or RS-423 port
connections for up to 16 asynchronous devices. They both have two port
connectors built directly into their backplanes, each of which can be
connected to a distribution panel which allows either all direct
connections or all modem connections. The DTC 16iX does not support
ARPA Telnet or X.25 connections. The DTC 16MX provides AFCP
connections for the HP 3000 environment and Telnet connections for
the ARPA environment; it does not support X.25 connections for wide
area networking. The DTC 16MX managed by an MPE/iX host is
limited to identical functionality as the DTC 16iX.