Compaq 281862-002 manual Data Compression, Response Codes, 8Additional Modem Information

6-8Additional Modem Information

Data Compression

Most high-speed modems also try to negotiate a compression protocol such as v.42 bis or MNP5 upon establishing a connection to another modem. Compression settings do not effect the ability to connect to IRC. However, negotiating such a protocol is advantageous, since it greatly accelerates responses from the server, particularly in remote console mode. Typically, compression is normally negotiated, unless it is explicitly turned off on either modem or the modems are incompatible. Typical AT commands to configure compression include &K, %C, &E, and S-Registersettings. Refer to your modem’s AT command reference for more details.

Response Codes

The way a modem responds to commands and events is also highly configurable. Through AT command strings, the modem can be instructed to communicate this information numerically or through verbal descriptions. For instance, based on its configuration, the modem may return “RING” in response to an incoming call, or the number 2. In addition, the modem can be configured return varying levels of information in several different formats.

Since modems vary greatly in how and what they send in response to event, IRC does not use modem response codes when communicating with the modem. Consequently, it does not matter what response code format it chosen or what is communicated in the response codes. IRC uses the modem control signals to determine events such as connect and ring.

Response code format commands are important, however, if you are sharing the modem with the operating system. In this case, IRC must have the modem configured to respond in a way that the operating system will expect and understand. See Appendix A for instructions in how to determine how the operating system has configured the modem under Windows NT 4.0.

There are several different AT commands on each modem to configure different attributes of the response codes. Typical AT commands used to configure the response codes include, V, \V, W, X, Q, &A, and S-register settings (particularly S95). Refer to your modem’s AT command reference for more details.