Dataplex DPX-213, User Manual

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BEFORE YOU START
Section 3
3-2
Copyright (C) Dataplex Pty Ltd
3.4 Dial-up Line and Leased Line Support
The DPX-213 cannot share the same line as your normal telephone. It can only be used in
isolation.
NOTE: Telephones with Mode 3 connectors should not be used with this equipment.
Contact Telecom if you are trying to use the modem on a small business key
system such as a Commander, as these hand sets often signal to the PABX
electronics with non standard tones and voltages. Damage to either the PABX or
the modem could result from incorrect connection. A direct line from the local
exchange may be needed in these situations.
Leased lines are special services providing a dedicated link between two sites. No
switching is involved and hand sets are rarely provided. The DPX-213 can be configured
to operate on two wire leased lines in synchronous or asynchronous modes. Special care
has been taken with the design to ensure reliable operation in leased line mode, particularly
with line changes caused by circuit re-routing. Section 5, Applications, details the
recommended set-up strings for this use. Leased line also requires modifications to the line
connector as shown in Appendix D.
3.5 Speed Matching
There are several forms of speed matching used in the DPX-213. The autobaud feature
automatically senses the terminal speed from the typed AT commands and sets the modem
interface speed to match the terminal. The autoranging feature automatically senses the
line speed of the remote modem and adjusts to it in both originate and answer modes.
Additionally, there is a Constant Speed Interface (CSI) on the DPX-213 modem which
allows your terminal to remain at the same speed, say 9,600 bps, for all 300, 1200 or 2400
bps full duplex calls. This simplifies operation with mini-computer systems provided you
support flow control and avoids data loss if there is a speed mismatch in the system.
3.6 Flow Control
Flow control is needed whenever one device in the system runs faster or slower than
another, or there are delays in transmission while errors are corrected. Flow control can be
In-band using Xon and Xoff characters or Out-of-band using Request To Send (RTS) and
Clear To Send (CTS). These are also referred to as software handshaking or hardware
handshaking. It is legitimate to have different flow control techniques at each end of the
link. The Xon and Xoff characters are user programmable in the DPX-213 and are stored
in S-Registers 32 and 33 respectively.