0049-2702-XXX Alliance Series Modems – USER MANUAL
08/05/2010
Rev. A
Page 14 of 197
2-Wire Dial V.25bis Mode
The ALX modem supports three types of V.25bis operation – asynchronous, synchronous character
oriented or synchronous bit oriented. There is a Quick Setup for each V.25bis type, as shown in
Table 1-1. For V.25bis operation,
the modem must be configured to use the same data protocol
(asynchronous, synchronous character oriented or synchronous bit oriented) –
as the attached DTE
.
If you have selected the correct V.25bis Quick Setup, the data protocol will be set automatically to
the correct setting. V.25bis mode operation and commands are explained in detail in Chapter 5.
Asynchronous V.25bis Operation
For asynchronous V.25bis operation, the data format of the DTE should be set to
7 data bits
with
even parity
and
one stop bit
. (Note that the default DTE interface rate is 38.4 Kbps in
asynchronous mode.)
In asynchronous applications, V.25bis commands (listed in Chapter 5) may be entered from the DTE
keyboard. For example, the simplest command sequence is
CRN 3331234
. In response to this
command, the ALX sends a VAL result code (indicating that the command has been accepted), dials
the telephone number, 333-1234, and then waits for an answer tone from a distant modem. If no
carrier is detected within a given time (45 seconds by default), the modem automatically releases the
line and sends a CFI NT result code.
When a call is successfully connected, the TIA/EIA status screen on the ALX will typically look like
this:
Synchronous V.25bis Operation
For synchronous V.25bis operation, set the data format of the DTE to
7 data bits
with
odd parity
.
In synchronous applications, the V.25bis commands can facilitate computer-controlled operations.
Synchronous bit-oriented operation uses High Level Data Link Control (HDLC) formatting. In
synchronous character-oriented operation, messages are framed by synchronous start-of-text and
end-of-text characters, with the start-of-text character preceded by two synchronous (SY) characters.
2-Wire Dial Dumb Mode
Dumb mode is used primarily for manual call origination, answer-only applications and in
conjunction with certain dial back security systems that utilize MI/MIC signals to place the modem
on-line. (If you need to configure the modem for MI/MIC use, refer to Appendix D).
After the Quick Setup for 2-wire dial Dumb mode has been selected, the ALX is configured to
automatically answer incoming calls. The only other requirement is that the DTE must provide the
DTR signal (TR on the TIA/EIA status screen) to the modem
or
DTR must be set to TRUE (using
the modem’s DTR from EIA option screen).
