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Chapter 4 - AT Commands, S-Registers, and Result Codes
Result Codes
When the MTA128ST-USB (TA) receives an A T command from the computer or terminal, it attempts to
execute the command, then sends a status message to the computer or terminal that reports the
result of the command. The TA provides you with several of these response messages, or

result

codes,

which can be displayed on your monitor or intercepted and used by your communications
software. Using the

V

command, you can select whether the result codes are

terse

(numbers) or

verbose

(words).
The TA’s result codes are listed below. Note that the speed of an ISDN channel is always either 56
Kbps or 64 Kbps.

Connect

messages indicate the speed of the connection between the TA and your
computer or terminal.
TERSE VERBOSE DEFINITION
0 OK TA executed the command without error
1 Connect TA established an ISDN connection
2 Ring TA detected a ring caused by incoming call
3 No carrier TA did not detect carrier within time allotted by S-
Register S7
4 Error Error in the A T command
5 Connect 1200 TA connected at 1200 bps
6 No dial tone TA has a poor connection to ISDN network
7 Busy TA detected a busy signal
9 Connect 600 T A connected at 600 bps
10 Connect 2400 TA connected at 2400 bps
11 Connect 4800 TA connected at 4800 bps
12 Connect 9600 TA connected at 9600 bps
14 Connect 19200 TA connected at 19200 bps
28 Connect 38400 TA connected at 38400 bps
56 Connect 56000 TA connected at 56000 bps
64 Connect 64000 TA connected at 64000 bps
P /PPP TA using Point-to-Point protocol
T /V.11 0 TA using V.1 10 rate adaption protocol*
V /V. 120 TA using V .120 rate adaption protocol
X /X75 TA using X.75 rate adaption protocol
* The MTA128ST-USB is manufactured in two builds. To determine the build of your terminal adapter
(TA), issue the ATI2 command in a terminal window. If the TA responds to the command with MTA128ST-
USB, then it supports V.110. If your TA resonds to the ATI2 command with MTA128ST-USB-RC, V.110
support is not available.