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T68i
White Paper, April 2002
28
Modem and AT
commands
TheT68icontainsacompleteGSM/GPRS
modem. This provides data and e-mail
communication, as well as Internet/intranet
access, for a connected PC, PDA or handheld
device. Once the PC/PDA is connected to the
phone using a cable, Bluetooth wireless
technology or infrared, and the appropriate
software is installed, the modem in the phone
works in a similar way to a PC Card modem, or an
external modem.
In the T68i, AT commands are used for:
• controlling the data communication
between the PC and the remote service
• configuring and requesting settings and
behaviours in the phone, from a connected
PC or PDA
GSM data communication
The built-in data capability turns the phone into a
modem when connected to a PC/PDA. The T68i
offers the user data connection anytime,
anywhere, unmatched by fixed telephone
networks. Each GSM channel is divided into eight
repeating time slots. A normal GSM voice or data
call is circuit switched, and only one time slot is
used for each call. The data speed is therefore
limited to 9,600 bps. For more information, see
“Built-in GSM data modem technical data” on
page 65.
High Speed Data gives a faster speed
High Speed Data (HSCSD) increases speeds for
circuit switched data by allowing the phone to
use a coding scheme with a high capacity, and to
use two time slots for receiving data. The
download speed is increased to up to 28,800
bps. The speed for sending data is limited to
14,400 bps. The data rate can be increased
several times by the use of rate adaption,
interworking with ISDN. This also provides
additional features, such as quick call set-up
capability.
GPRS enables constant connection
and high speed
With GPRS, the connection is maintained
“constantly”, and data is transmitted in packets.
Pricing of GPRS can be dependent on the actual
use of bandwidth, which means very low cost
when no data is sent or received, while the phone
remains connected. When transmitting large
amounts of data, bandwidth can be increased
automatically to allow faster transmission speed,
up to 64,200 bps download speed.
AT commands support
This section outlines the AT commands
supported by the T68i. The information here can
be of use for advanced users, to indicate the
possibilities they have to:
• develop new communications software
• add the T68i to an application’s list of com-
patible modems
• adjust the settings of their mobile tele-
phone and modem
The modem in the T68i supports the V.25ter
command set, which is the standard
communication set used by modems.
TheT68iiscompatiblewithindustrydefacto
extensions, ETSI 07.05, 07.07 and 07.10.
Overview of AT command functions
AT commands are used to configure the mobile
telephone, to request information about the
current configuration or operational status of the
mobile phone, and to test availability and request
the range of valid parameters, when applicable,
for an AT command.
The built-in modem can be set to any one of three
modes of operation. These are:
Off-line command mode
The command mode for entry of AT commands,
when the device is first turned on.
On-linedatamode
Allows “normal” operation of the built-in modem,
for exchanging data or facsimiles with a remote
modem.
On-line command mode
For sending AT commands to the built-in modem
while remaining connected to a remote modem.