NETGEAR XM128 ISDN manual Terminal Adapter or Digital Modem, Isdn Basic Rate Interface Points

Reference Guide for the Model XM128 ISDN Digital Modem

The B channels are used for carrying user communication information, which can be data, voice, or fax. Voice and analog data must be sent on the B channels. Unlike the asynchronous communications between most PCs and your Model XM128 modem, the B channel operates in synchronous mode. In order to convert the asynchronous communication to synchronous communication, it is necessary to use a Rate Adaption Protocol.

In North America, the V.120 Protocol is the most popular Rate Adaptation Protocol used. The V.120 Protocol is an ITU-T protocol that supports synchronous and asynchronous rate adaption and provides link-layer error control. NETGEAR also implements V.42bis data compression on top of V.120, allowing the user to achieve even higher data communication throughput.

The Model XM128 modem also supports high-level data link control (HDLC) asynchronous to synchronous conversion from Point-to-Point Protocol (PPP). This protocol is very popular for Internet access and remote access applications.

Currently, most of us still use plain old telephone service (POTS) for our regular communication needs. The Model XM128 modem provides two POTS ports (PHONE 1 and PHONE 2) for you to connect analog devices; this feature lets you continue to use analog communications. You can connect phones, fax machines, or analog modems to the PHONE 1 and PHONE 2 ports, while using one of the idle B channels (even if the Model XM128 modem is busy doing data communications).

Terminal Adapter or Digital Modem

A terminal adapter (TA) allows users to send and receive data over the ISDN network. You can send and receive both data and voice simultaneously by using both B channels. The PHONE 1 and PHONE 2 ports in the Model XM128 modem allow you to connect analog devices to the modem to make outgoing calls as well as to receive incoming calls. With its auto-detect feature, the Model XM128 modem monitors incoming calls from both analog and digital devices. It monitors these calls without user intervention and makes connections accordingly.

ISDN Basic Rate Interface Points

In the interest of supporting deregulated Customer Premises Equipment (CPE), the exchange Carrier Standard Association in the United States established a basic rate transmission standard for CPE. The standards are defined for equipment to connect to different reference points of the ISDN link. Some of these reference points are S, T, and U. They have very specific definitions and provide standard interfaces for equipment connected to them.

ISDN Reference G-3