Miscellaneous Commands - Multitech MT2834MR Owner's Manual

PN 88300150
$MI MI/MIC Control
The $MI command enables and disables the mode indicate/mode indicate common interface
function. AT$MI1 enables MI/MIC operation and AT$MI0 disables it.
With the MI/MIC option enabled, the modem's A and A1 telephone line interface output leads
are replaced with MI and MIC input leads. (Tip and Ring remain unaffected.) When MI and
MIC are connected together, the modem goes Off Hook in Originate mode, for a time period
specified by the modem's Abort Timer (S-Register S7). For example, a 45 second Abort
Timer means that if the modem does not detect a carrier tone within 45 seconds after it goes
Off Hook, it will disconnect.
The $MI command is not available on the MT2834MRK.
Note: This option is a hardware modification that must be ordered separately; it is not
automatically included with the MT2834MR modems.
&T Enable or Disable Recognition of Remote Digital Loop Signal
The MT2834MR has several test features, which are covered in detail in Chapter 6. The tests
are activated with different U commands, such as ATU0, ATU1 and so forth. There is one
command, however, that is really a configuration command, so we will cover it here. That is
the &T command, which enables or disables the modem's ability to recognize the Remote
Digital Loop (RDL) test signal.
The command AT&T4 allows the MT2834MR to respond to a RDL signal, and place itself in
digital loop. The command AT&T5 disables this capability, meaning that the modem will
ignore the RDL signal. (Refer to Chapter 6.)
#T Enable/Disable Trellis Coded Modulation
The #T command enables or disables Trellis Coded Modulation for the MT2834MR. There is
usually no need to disable (turn-off) Trellis Coded Modulation except under an unusual line
condition called impulse noise. The command AT#T0 turns off Trellis Coded Modulation and
AT#T1 turns it on. The factory default setting is AT#T1.

3.9.5 Miscellaneous Commands

&A Answerback
The &A command controls the MT2834MR's Answerback feature. Answerbacks are used in
some on-line realty applications, and elsewhere, as a security measure. Due to the security
aspect of this feature and the fact that there is no requirement for the user to do anything with
the modem, we will not discuss Answerback here, other than to say that it exists and that we
recommend you avoid &A in any commands or programming.
&B Transmit Buffer Size
The size of the transmit buffer size is controlled with the &B command. It may be desirable to
reduce the size of the transmit buffer for certain applications. For example, when your
modem is receiving a long stream of data and the modem at the other end is using speed
conversion (the serial port speed is greater than the modem baud rate). If you wanted to
interrupt the current data and request data from a new source, you may have to wait for data
in the buffer of the sending modem to empty. By reducing the transmit buffer size of the
sending modem, this wait will be reduced. Using the reduced buffer size may cause a slight
loss in data throughput.
AT&B0 = Normal transmit buffer size
AT&B1 = Reduced transmit buffer size
The factory default setting is &B0
4/3/01 35