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The main purpose of this TCS was to introduce the students to ISDN. They learned how ISDN functioned, how it is installed, comparative rate of speed compared to other services. There were also learning objectives such as ISDN reference points and the five devices related to ISDN installation.

The main learning objectives of the TCS were the following:

1. Describe the user requirements for implementing ISDN to a site.

There are really only two things required to implement ISDN to a site. An ISDN capable router and the remote user software. The router will usually be on the service providers side and the remote user software will be on the users side.

2. Describe the different ISDN standards and protocols.

Protocols beginning with "Q" cover how switching and signaling should operate. The term "signaling" in this context means the process of call set up used. Q.921 describes the ISDN data-link processes of LAPD, which functions like Layer 2 processes in the OSI reference model. Q.931 specifies ISO/OSI reference model layer 3 functions.

Protocols that begin with "I" deal with concepts, terminology, and general methods. The I.100 series includes general ISDN concepts and the structure of other I-series recommendations; I.200 deals with service aspects of ISDN; I.300 describes network aspects; I.400 describes how the User-Network Interface (UNI) is provided.

Protocols that begin with "E" recommend telephone network standards for ISDN. For example, the E.164 protocol describe international addressing for ISDN.

3. Describe the five major devices in an ISDN implementation.

1. Terminal Equipment 1 (TE1) - Designates a device that is compatible with the ISDN network. A TE1 connects to a Network Termination or either Type 1 or Type 2.

2. Terminal Equipment 2 (TE2) - Designates a device that is not compatible with ISDN and requires a Terminal Adapter.

3. Terminal Adapter (TA) - Converts standard electrical signals into the form used by ISDN so that non-ISDN devices can connect to the ISDN network.

4. Network Termination Type 1 (NT1) - Connects 4-wire ISDN subscriber wiring to the conventional 2-wire local loop facility.

5. Network Termination Type 2 (NT2) - Directs traffic to and from different subscribe devices and the NT1. The NT2 is an intelligent device that performs switching and concentrating.

4. Describe the four major reference points in an ISDN implementation.

1. R - References the point (connection) that is a non-ISDN compatible device and a Terminal Adapter.

2. S - References the points that connect into the NT2, or customer switching device. It is the interface that enables calls between the various customer premises equipment.

3. T - Electrically identical to the S interface, it references the outbound connection from the NT2 to the ISDN network.

4. U - References the connection between the NT1 and the ISDN network owned by the phone company.

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