For AVAYA, NORSTAR, NEC, SAMSUNG, MITEL, PANASONIC, TOSHIBA T.646.872.2025 . . . Embended voicemail R3.1 (65) Avaya S8710 Media Server with Avaya G650 Media Gateway Avaya Communication Manager R3.1.1 (R013x.01.1.628.7) Avaya 4621SW IP Telephone R2.3 Avaya 5610SW IP Telephone R2.2 Avaya 5410 Digital Telephone N/A Avaya 2420 Digital Telephone N/A Avaya 6211 Analog Telephone N/A Avaya C363T-PWR Switch R4.1.4 Cisco 3825/2811 routers. offered by regional telephone carriers. ISDN involves the digitization of the telephone network, which permits voice, data, text, graphics, music, video, and other source material to be transmitted over existing telephone wires. The emergence of ISDN represents an effort to standardize subscriber services, user/network interfaces, and network and internetwork capabilities. ISDN applications include high-speed image applications (such as Group IV facsimile), additional telephone lines in homes to serve the telecommuting industry, high-speed file transfer, and videoconferencing. Voice service is also an application for ISDN. This chapter summarizes the underlying technologies and services associated with ISDN devices include terminals, terminal adapters (TAs), network-termination devices, line-termination and exchange-termination equipment. ISDN terminals come in two types. Specialized ISDN terminals are referred to as terminal equipment type 1 (TE1). Non-ISDN terminals, such as DTE, that predate the ISDN standards are referred to as terminal equipment type 2 (TE2). TE1s connect to the ISDN network through a four-wire, twisted-pair digital link. TE2s connect to the ISDN network through a TA. The ISDN TA can be either a standalone device or a board inside the TE2. If the TE2 is implemented as a standalone device, it connects to the TA via a standard physical-layer interface. Examples include EIA/TIA-232-C (formerly RS-232-C), V.24, and V.35. Beyond the TE1 and TE2 devices, the next connection point in the ISDN network is the network termination type 1 (NT1) or network termination type 2 (NT2) device. These are network-termination devices that connect the four-wire subscriber wiring to the conventional two-wire local loop. In North America, the NT1 is a customer premises equipment (CPE) device. In most other parts of the world, the NT1 is part of the network provided by the carrier. The NT2 is a more