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AT Command Set Operation
AT Command Details
This section provides special considerations and detailed lookup tables for certain AT commands.
\Tn Command - Special Considerations
The \T n command controls the DTE speed, in conjunction with the switched network handshake
mode command (&Hn). There are several factors to consider when setting this value:
•
An automatic handshake mode (e.g., V.32 bis auto &H1 , V.32 auto &H4 , V.22 bis only &H6 )
takes precedence over the \Tn selection. The modem will try for the highest VF speed
common to the two commands.
•
For 1200 bps V.22 operation, select &H7 . Since &H6 is an auto mode, setting the DTE to
1200 bps with the \T3 command will not force the connection to 1200 bps.
•
When the modem is optioned for an automatic handshake mode and direct V.14 asynchronous
mode ( \N1 ), it sends a connect message to the DTE at the selected \Tn speed. In order to pass
data, the user must change the DTE's speed to match the displayed connect speed.
•
When the modem is optioned for speed buffering ( \N0 ) or an error correcting protocol ( \N2
through \N5 ), the \Tn command alone selects the DTE speed. The &Hn command selects
the handshake mode.
•
When the modem is optioned either for a fixed handshake mode and direct mode ( \N1 ) or for
synchronous data mode ( &M1 ), the \Tn command not only selects the DTE speed, but also
forces the VF speed to match it. If this speed is not available, the modem drops the call.
This does not apply to V.22 bis only, which handshakes at the highest VF speed.)
•
When using the modem in direct mode ( \N1 ), if the desired connect speed is known, set the
speed to match, using the \Tn command. Set the DTE to the same speed and then AT the
modem so that it will know at what speed to send messages.
Asymmetrical DCE Rates - Special Considerations
•
Asymmetrical rates are disabled by the AT commands: \N1 , \N6 and %M1
•
The &G command limits only the rate of the receiver in \R1 mode.
•
The \V0 and |V2 command formats remain the same reporting the receivers rate.
•
The \V1 and \V3 commands report the DTE rate. The \V4 commands reports the
Asymmetrical rate.
•
Front Panels report the Receive Rate (single rackmount).
4-22
SpectraComm Dual V.34 Modem
Installation and Operation
AT Command Details
060R122-000
Issue 15
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