ZyXEL Communications U-336R/RE manual Basic Modem Operation, Understanding AT Commands

3 Basic Modem Operation

This chapter covers the basic commands and techniques involved in modem operation. In many cases, this is the only information you will need in order to get up and running with communication software, and to start making connections with your modem.

Understanding AT Commands

The U-336R/RE communicates asynchronously with computers using AT commands. AT commands are used to configure and control your modem. Commands are usually sent to the modem by way of communication software, but can also be entered manually by the user with the computer keyboard.

Command statements must be written in a specific form in order for your modem to recognize them. A command statement always begins with the letters AT or at. It is then followed by one or more commands and the <Enter> key.

AT commands can only be issued when your modem is in “command mode” or “off-line.”

Once your modem has established a connection with another modem it is said to be “on-line” or in “data mode.” In this mode, the characters sent to your modem by your computer are transmitted to the remote modem rather than being interpreted by your modem as commands.

Using the Windows 95 Hyper Terminal Program

In order to issue an AT command statement, you first need to run a communication program such as Microsoft Windows “Hyper

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