Multi-Tech Systems MTA128ST-USB - Manual (Page 66)

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MultiModemISDN User Guide
MTA128ST-USB
Data is being lost
• USB cable is not plugged in.
• Make sure the flow control method you selected in software matches the method
selected in the MTA128ST-USB.
Making a V.120 call, caller gets a NO CARRIER message after dialing the
number
Some switches don’t support ISDN SETUP messages that contain a LLC (low layer
compatibility) element. When these switches receive an LLC in the SETUP, they
immediately reject the call and a NO CARRIER message displays. Disable LLC for V.120
calls by issuing the command AT!D0=0. To enable LLC for V.120 calls, issue the
command AT!D0=1.
Making a V.110 call, caller gets a NO CARRIER message after dialing the
number
Some switches don’t support extended BC (bearer capability) information in the ISDN
SETUP message, such as the one normally sent by V.110 data protocol. When these
switches receive a BC with extended capability information in the SETUP, they
immediately reject the call and a NO CARRIER message displays. Disable sending
extended BC information for V.110 calls by issuing the command AT!D1=0. To enable
sending extended BC information for V.110 calls, issue the command AT!D1=1 (the
default setting).
When using X.75 data protocol to transfer data via the Zmodem, the Zmodem displays
Intermittent bad packet errors and data throughput drops.
This occurs in cases when the X.75 packet size is greater than 1024 bytes and the
terminal adapter sending the file has a fast baud rate (e.g., 115200 bps) or its a USB TA,
and the terminal adapter receiving the file has a slow baud rate (e.g., 19200 bps). To
reduce or possibly eliminate this, reduce the X.75 packet size (S53) to a value less than
or equal to 1024 bytes (e.g., ATS53=512). However, if you set the receiving terminal
adapter’s baud rate nearly equal to or greater than the baud rate of the sending terminal
adapter, then the packet size can be greater than 1024, and Zmodem transfers the data
without bad packet errors.
The MTA128ST-USB won’t accept V.120 calls from a 3Com Impact IQ
terminal adapter. The Impact IQ displays a connected status, but the
MTA128ST-USB does not.
The MTA128ST-USB is looking for a SABME command from the Impact IQ to finish
establishing the V.120 connection. However, the Impact IQ won’t send a SABME until it
has data to send. Have the Impact IQ send a character by pressing any key (such as the
space bar) on the terminal attached to the Impact IQ. The MTA128ST-USB responds with
a CONNECT message and displays the key you pressed (e.g., a space).