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General Modem Commands How to Use These Commands Error Correction Commands Data Compression Commands

Modem Commands***

***Note:   This document is offered for informational support only. No active technical support or document revisions will be made after the date noted at the bottom of the document.

General Modem Commands

• ATI0 is an information command, often returning the modem's speed.
• ATI3 and ATI4 are also information commands, often returning the modem's manufacturer and model.
• ATI7 will often provide advanced modem information, such as ROM updates.
• ATZ will return the modem to the default settings.
• ATDT*70 will disable call waiting.

How to Use These Commands

The PC communicates with the modem using a command set, often referred to as the AT Command Set. These commands can be used to configure, diagnose and receive information from the modem. Modem commands can either be used as part of an initialization string in a specific program, or can be issued directly to the modem using one of the following programs, depending on your operating system.

Windows 98/Me/2000/XP Users

1. Select Start > Programs > Accessories > Communications > Hyperterminal.

2. Double-click hypertrm.exe.

3. Enter Terminal Mode in the Name field, then click OK.

4. Do not enter a phone number in the next box. Instead, click on the drop-down arrow on the Connect Using field.

5. Select Direct to COM X, where X is the port the modem is on.

6. Click OK.

7. Click OK once more, and a terminal screen will appear, where modem commands can be typed.

Windows 95/NT Users

1. Select Start > Programs > Accessories > Hyperterminal.

2. Double-click hypertrm.exe.

3. Enter Terminal Mode in the Name field, then click OK.

4. Do not enter a phone number in the next box. Instead, click on the drop-down arrow on the Connect Using field.

5. Select Direct to COM X, where X is the port the modem is on.

6. Click OK.

7. Click OK once more, and a terminal screen will appear, where modem commands can be typed.

Error Correction Commands

Error correction helps cut down on noise and other phone line problems, which will result in less data loss. The packet design of error correction can also lead to greater throughput.

Despite the benefits, in some cases, it is necessary to disable error correction. Connecting to an old 2400 modem, which cannot perform error correction, would be one such case.

To disable error correction:

• For US Robotics Modems, use the command AT&M0
• For Rockwell Modems, use the command AT\N0
• For Hayes Modems, use the command &Q6

Data Compression Commands

Besides error control protocols, all current high-speed modems also support data compression protocols. That means the sending modem will compress the data on-the-fly and the receiving modem will decompress the data to its original form.

In some cases, it is necessary to disable data compression.

• For US Robotics Modems, use the command &K0
• For Rockwell Modems, use the command %C0
• For Hayes Modems, use the command ATS110=0