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Installing Your Modem

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AT Commands,
S-Registers, and
Result Codes

Regulatory Information

USRobotics 56K PC Card Modem User Guide


Modem Features

  • Advanced Line Probing: Advanced Line Probing technology for V.90 connections automatically steers you around even the worst line impairments, allowing faster connections and data transfers.

  • AT Command Help Screens: AT commands allow you to control many of the functions of your modem. You can use AT commands by typing them at the command line of any Terminal program. Your modem can display screens summarizing AT commands, dial command options, and S-register functions. Refer to the AT Commands, S-Registers, and Result Codes section in this guide.

  • Automatic Calling Card Dialing: Whenever you make a calling card call, your modem will detect the tone that sounds prior to entering your calling card number. You can have the modem automatically enter your calling card number and place the call by entering the following string: ATDT <phone#>&<calling card#>

  • Call Progress Detection: An optional set of result codes lets you know when the telephone number you have dialed is busy, the line has been picked up but a modem is not answering the call, there is no dial tone on the telephone line, or a call is coming in. These result codes, and the commands that enable or disable these result codes, are controlled by the ATXn command. Refer to the AT Commands, S-Registers, and Result Codes section in this guide.

  • Caller ID: If you live in North America, your modem allows you to identify callers' names and telephone numbers when they call. Your communications software must support this feature, and you must subscribe to Caller ID from your phone company. Use AT#CID=1 to manually turn on Caller ID and set S0=2 because Caller ID is received between the first and second rings.

  • Dialing Stored Phone Numbers: Your modem can store up to four of your most frequently called numbers. Refer to the AT Commands, S-Registers, and Result Codes section in this guide.

    Use AT&Z for storing numbers and ATDS for dialing stored numbers. For example, suppose you are dialing a phone number of 123-4567, and it is the first number you have stored. You would enter AT&Z0=1234567 to store the number, and ATDS0 to dial it. To dial the second phone number in the stored numbers list, you would enter AT&Z1=9876543 to store it, and ATDS1 to dial it.

  • Digital Line Guard: For landline connections, Digital Line Guard protects the modem's circuitry from overvoltage from ISDN or digital PBX lines.

  • Redialing the Last Dialed Number: Your modem stores each dialed number until another number is dialed. Enter ATDL to redial the last number dialed during the current session.

  • Software Upgrade: Your modem can be updated to correct problems without having to return your modem to USRobotics. Current software upgrades and the instructions to use them are available from the U.S. Robotics Web site at If your modem is functioning properly, there is usually no need to upgrade it. In any case, we recommend upgrading only under the direction of a Customer Support Application Engineer.

  • V.90 Technology: With V.90, your modem will be capable of receiving data at up to 56 Kbps and sending data at up to 31.2 Kbps.
  • *Actual download speeds you experience may be lower due to varying line conditions. Requires compatible phone line and server equipment. Complies with both the V.90 56K standard and x2 technology protocol.


What You Will Need

  • Notebook computer with an empty PC card slot
  • Analog telephone line

CAUTION: The USRobotics 56K PC Card Modem requires a standard analog telephone line. Do not connect your modem to a digital telephone line. Digital lines are commonly used in office buildings and hotels. If you are unsure whether your line is analog or digital, ask your network administrator, building management, or your local telephone company.


Before You Begin: Preparing for installation

Note: USRobotics recommends uninstalling any other modems that are installed in your system and unplugging all telephone cords connected to these modems. Refer to your previous modem's documentation for instructions.

Write down your new modem's serial number, which is located on the white bar code sticker on the modem and on the modem's box, in the Quick Installation Guide. If you ever need to call our Technical Support department, you will need the serial number and the model number (0756) to receive assistance. If you need to get assistance or download drivers from the Web site, you will need the product ID (USR0756-CB or USR0756-XJ).

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