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How the Device Initializes USB Modems

When you connect the USB modem to the USB port on the Services Router, the device applies the modem AT commands configured in the init-command-string command to the initialization commands on the modem. For more information about configuring modem commands for the init-command-string command, see Modifying USB Modem Initialization Commands.

If you do not configure modem AT commands for the init-command-string command, the device applies the following default sequence of initialization commands to the modem: AT S7=45 S0=0 V1 X4 &C1 E0 Q0 &Q8 %C0. Table 53 describes the commands. For more information about these commands, see the documentation for your modem.

Table 53: Default Modem Initialization Commands

Modem Command	Description
AT	Attention. Informs the modem that a command follows.
S7=45	Instructs the modem to wait 45 seconds for a telecommunications service provider (carrier) signal before terminating the call.
S0=0	Disables the auto answer feature, whereby the modem automatically answers calls.
V1	Displays result codes as words.
&C1	Disables reset of the modem when it loses the carrier signal.
E0	Disables the display on the local terminal of commands issued to the modem from the local terminal.
Q0	Enables the display of result codes.
&Q8	Enables Microcom Networking Protocol (MNP) error control mode.
%C0	Disables data compression.

When the Services Router applies the modem AT commands in the init-command-string command or the default sequence of initialization commands to the modem, it compares them to the initialization commands already configured on the modem and makes the following changes:

If the commands are the same, the device overrides existing modem values that do not match. For example, if the initialization commands on the modem include S0=0 and the device’s init-command-string command includes S0=2, the Services Router applies S0=2.
If the initialization commands on the modem do not include a command in the device’s init-command-string command, the device adds it. For example, if the init-command-string command includes the command L2, but the modem commands do not include it, the device adds L2 to the initialization commands configured on the modem.

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