T1 fundamentos

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T1-Service

Digital Link Presents:

T1 FRAME

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DS0

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1 1

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T1 Fundamentals

1 Revision 1.0 01-23-97

T1 Fundamentals

i Copyright © 1996, Digital Link Digital Link Corporation World copyright reserved. No part of this publication may be stored in a retrieval system, transmited, or reproduced in any way, including but not limited tophotocopy, photograph, magnetic, chemical, or other record, without the prior agreement and written permission of Digital Link Corporation. Digital Link Corporation 217 Humboldt Court Sunnyvale, California 94089 (408) 745-6200 FAX (408) 745-6250

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T1 Fundamentals

Course Objectives:
Upon completion of this course the student will be able to: • • • • • • • • • • •Understand the basic T1 transmission concepts Understand how the T1 frame is constructed. Discern the differences between ESF and SF framing formats. List the main benefits of the ESF framing format Be able to accurately match ESF error events with their functions. Understand how ESF registers are used in trouble isolation Describe T1 alarm states (Blue, Yellow, Red). Understand the wiring that isused on T1 lines and cables that are used. Define the coding methods used on T1 circuits (B8ZS and AMI) Understand the differences between format and logic errors. Understand T1 troubleshooting techniques and equipment

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Concepts Behind T1

What is T1?
A T1 is a Time Division Multiplexed, full duplex, synchronous data transmission technique. It has an operationalline data rate of 1.544Mbps. Below is a list of general information that applies to a T1 line. Time Division Multiplexing (TDM) is a means to carry multiple voice and data conversations across a single line. It is a very reliable means of communications as it a allows time slots to be dedicated to each conversation (be it voice, data, fax or video). On the other hand, it is inefficient since if onlya few time slots are needed the unused time slots will be idle. This will be discussed further later. Full duplex operation is a method of transmission that enables information to be both transmitted and received at the same time. The aggregate speed of a T-1 is 1.544Mbps. Only 1.536Mbps is usable as 8kbps is used for overhead. Fractional T-1 is supported by the telephone carriers as a method toreduce cost to their customers. Some customers don’t need to use all time slots on a T-1, so FT1 is a way to get greater efficiency using TDM to pay only for the number of time slots you need. DS1 is the tariffed service from the carriers. DS refers to Digital Signal and has references at different levels such as: DS0 (64Kbps), DS2(6Mbps) and DS3(45Mbps). It defines the type of service that thecustomer will receive, the costs and the signal format. T-1 is what the DS1 signal becomes when it is placed on a “Terrestrial” line.

4 Revision 1.0 01-23-97

Concepts Behind T1

What is T1?
• • • • • • Multiplexing of 24 Voice/Data Channels Full duplex four wire facility Operates at 1.544Mbps Supports fractionalized services All major carriers provide service DS1 Vs. T1

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Concepts Behind T1

T-1 Transmission Concepts
Nyquist CriterionHarry Nyquist discovered in the late 1920’s that in order to sample an analog signal so that it can be represented in a digital format (and later be reconstructed back to it’s original form) that the analog signal needs to be sampled at twice the highest frequency of the analog signal. Since the average human speakswithin the frequency range of 300-3300hz(cycles/sec), it was decided that the maximum frequency to represent a voice signal should be 4000hz. When we apply this to the Nyquist’s theorem we discover that the minimum sampling rate necessary to digitize an analog signal of 4000hz is 2X4000hz=8000hz=8000samples/sec.

PAMWhen an analog signal is sent through a sampler device it will create a digital...
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