Connecting to your ISP

Using the AT Command Set

Upgrading your Modem

Modes of Operation

Dialing, Answering, and Hanging Up

Working with Memory

Controlling Result Code Displays

Controlling EIA-232 Signaling

Accessing and Configuring the Courier 56K Corporate Modem Remotely

Controlling Data Rates

Dial Security

Flow Control

Handshaking, Error Control, Data Compression, and Throughput

Displaying Querying and Help Screens

Testing the Connection

Dedicated/Lease Line and Synchronous Applications




Alphabetic Command Summary

Flow Control Template

Result Code Meanings and Sets

Technical Information

V.25 bis Reference


Fax Information for Programmers

Viewing LEDs

Regulatory Information


Courier 56K Corporate Modem Command Reference

Modes of Operation

This chapter contains information about:

Command and Online Modes

If you want to
Set the modem to
Use this command

Control the modem using AT commands.

Depending on how DIP switch 9 is set, sending the escape code (+++) will return the Courier 56K Corporate modem to Command Mode or hang up. To be able to change operating modes without losing connections, set DIP switch 9 down.

Command Mode
+++ (Escape Code)
Set your modem to revert to Command Mode when the Escape Code (+++) is used.
DIP switch 9 DOWN
Set your modem to Disconnect when the Escape Code (+++) is used.
DIP switch 9 UP
Return to your connection after an Online Command Mode session.
Online Mode
Send the modem commands while you are on line with another device.
Online Command Mode
+++ (Escape Code)

Note: Do NOT type AT before +++ or Enter after the command

Entering Online Command Mode

When the modem is in Online Mode, the only command it recognises is an escape code, or +++.

Revert to Command Mode without losing connections by using setting DIP switch 9 down or sending ATS14.0=0 to the modem before establishing your connection.

  1. Wait one second after sending the last item of data.
  2. Type +++
  3. Wait for OK to appear before typing any data.

You can change the characters used to revert to Command Mode or the wait time by resetting Register S2 or S12. For more information about resetting these S-Registers, refer to the S-Registers chapter in the Appendixes section.

Returning to Online Mode

There are two ways to return online using the ATOn command.

If you want to
Return online
Return online and retrain

Example: Sending ATO1, will allow you to resynchronise if you experienced errors during a non-ARQ data transfer.


Controlling Local Echo

There are two local echo settings, one for Command Mode and one for Online Mode.

Command-Mode Local Echo

You can configure your modem to display the commands you type onscreen by using the ATEn command.

If you want the commands you type to
NOT appear on screen (Command Mode echo OFF) ATE0
Appear on your screen (Command Mode echo ON) ATE1

Note: Although you cannot see the command when you set ATE0, the modem is receiving them. The “E” command is set according to DIP switch 4.

Online-Mode Local Echo

To configure your modem to display a copy of data that is being transmitted on your screen you can use the ATFn command.

As the modem transmits data to a remote system
The modem sends a copy of the data to the screen. Online local echo ON (half duplex).
No copy of the data is displayed on screen. Online echo OFF (full duplex).
ATF1 (default)

Example: Sending ATF0 will allow you to see what you are typing in the display window.

Note: You may see the term "duplex" used in place of online local echoing, although the term is not technically accurate.


Data and Fax Modes

Once you are in Command Mode, you can initialise the modem in Data or Fax mode.

Fax operations require facsimile-compatible communications software that can send or receive Group III faxes. Follow the instructions in your fax software manual.

Note: The modem's default operating mode is Data Mode. Most fax software automatically switches the device to Fax mode when you run the program and resets the device to Data mode when you exit the program.


If you want the modem prepared to
Make calls to and receive calls from other modems
Data Mode
Make calls to and receive calls from analogue facsimile devices, such as fax modems and fax machines
Fax Mode
AT+FCLASS=1 (Class 1 Fax Mode)
AT+FCLASS=2.0 (Class 2.0 Fax Mode)

Example: Sending AT+FCLASS=1, allows you to receive faxes from fax machines.

Note: Class 1 and Class 2.0 Fax Modes refer to standards set by the Electronic Industries Association/Telecommunications Industry Association. Class 1 Fax Mode is the minimal standard for computer-faxmodem interface. Class 2.0 Fax Mode refers to the extended computer-faxmodem interface.

If you are not sure whether your modem is in Data or Fax mode, use the AT+FCLASS? command.

If the modem returns a value of
This indicates
Data Mode
Class 1 Fax Mode
Class 2.0 Fax Mode.

Note: Whenever the modem is reset using the ATZ command or by turning the power off and then on, it will reset to Data Mode.