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Chapter 10 − Modem Mode AT Commands, S-Registers, and Result Codes
Multi-Tech Systems, Inc. MultiConnect Serial-to-Serial Adapter User Guide (S000354A) 127
Result Codes
The modem responds to commands from the DTE and to activity on the line by signaling to the DTE in the form of
result codes.
Two forms of each result code are available:
• Short-form – a data-like numeric response (included in parentheses following the long-form). The short-form
is terminated by < CR> only with no preceding sequence.
• Long-form – a "verbose" response, preceded and terminated by the sequence < CR> < LF>.
If result messages are suppressed, nothing is returned to the DTE.
The long-form result codes can be modified by the OEM through the .INF file.
The Verbose response may differ in some instances. Some modems may use V.90 terminology and some may use
V.92 terminology; however, the meaning of the message is the same:
V.92 Terminology V.90 Terminology
+MRR Carrier
+DR Compression
+ER Protocol
+MCR Connect
Note: An asterisk (*) in the Short Form column means that this Result Code is not active in V.22bis modems.
Table of Result Codes
Short
Form
Long Form Description
+F4 * +FCERROR
Fax data speed. High speed fax data (V.27, V.29, V.33, or V.17) is expected but a V.21
signal is received.
0 OK
Command executed. A command has been executed.
1 CONNECT
Modem connected to the line. For X command values specifying no speed reporting,
the modem has connected to the line and either the line speed is 300 bps and line speed
is enabled, or the DTE speed is 300 bps and DTE speed reporting is enabled.
2 RING
Ring signal detected. An incoming ring signal is detected on the line. What qualifies as
a ring signal is determined by country-dependent parameters, modifiable through patch
code.
3 NO CARRIER
Carrier signal lost/not detected. Sent when attempting to establish a call if:
1. Ringback is detected and later ceases but no carrier is detected within the period of
time determined by register S7, or
2. No ringback is detected within the period of time determined by register S7.
Also sent when the modem auto-disconnects due to loss of carrier.
For X0, sent for the following conditions:
1. If busy tone detection is enforced, busy or circuit busy has been detected.
2. If dial tone detection is enforced or selected, dial tone has not been detected.
4 ERROR
Invalid command. Sent during an attempt to execute a command line if any of the
following conditions occur:
1. The command line contains a syntax error.
2. The modem cannot execute a command contained in the command line, i.e., the
command does not exist or is not supported.
3. A command parameter within the command line is outside the permitted range.
For X0, X1, X2, and X3, this message is sent instead of DELAYED and BLACKLISTED.
5 CONNECT1200
Connected at 1200 bps. The modem has connected to the line and either the line
speed is 1200 bps and DCE speed reporting is enabled, or the DTE speed is 1200 bps
and DTE speed reporting is enabled.
6 NO DIAL TONE
No dial tone detected. For X2 and X4, the modem has been instructed to wait for dial
tone during dialing but none is received.
7 BUSY
Busy signal detected. For X3 and X4, if busy tone detection is enforced, the busy
signal is detected on the line when the modem is attempting to originate a call.
8 NO ANSWER
No answer at remote end. The modem is attempting to originate a call if a continuous
ringback signal is detected on the line until the expiration of the timer S7.
9 CONNECT 600
Connected at 600 bps; speed reporting enabled. The modem has connected to the
line, the DTE speed is 600 bps, and DTE speed reporting is enabled.
10 CONNECT 2400
Connected at 2400 bps; speed reporting enabled. The modem has connected to the
line and either the line speed is 2400 bps and DCE or DTE speed reporting is enabled.