NETGEAR XM128 ISDN - Manual (Page 52)

Reference Guide for the Model XM128 ISDN Digital Modem
6-4 ISDN Overview
Commands for Incoming Calls
When a call comes in, the call is carried by one of the following protocols:
• V.120
• HDLC PPP, MPPP, or SLIP
• V.110
• X.75
Or the call may be initiated by an analog device.
This section provides some general guidelines for setting up the Model XM128 modem for call
answer handling. Be aware that the modem does not automatically answer a call unless S-register
S0 is set to a value greater than 0 (zero). If S-register S0=0, the modem only reports RING to your
terminal program. It can also respond with an audible tone that allows you to decide whether or not
you should take any action.
When an ISDN data call comes in, the Model XM128 modem tries to negotiate a connection using
the proper ISDN protocol. When an analog call comes in, the modem sends the call to the analog
port as the factory default, PHONE 1, and then PHONE 2.
Digital Data
The Model XM128 modem currently supports Circuit Switched Data (CSD) for ISDN data
applications. The CSD protocols supported by the Model XM128 modem include: PPP, MPPP,
V.120, X.75, and V.110. PPP is the most popular protocol used in North America; it is used by
most of the Internet service providers. After the Model XM128 modem answers a call, it examines
the incoming data to determine which protocol to use and automatically switches to that mode.
This process occurs transparently to the user. The Model XM128 modem is able to auto-switch for
PPP, MPPP, V.120, X.75, and V.110 protocols over speech channel. In most cases, you can rely on
the auto-switching feature for your applications. If you need more specific settings for answering
calls, refer to “
Answering a Call Using MSN ” on page 5-5.