Analog Access to the Telephone Network - Courseware Sample

145 Pages·2015·1.15 MB·English

by  Festo Didactic

Telecommunications
Telephony
Analog Access to the Telephone Network
Courseware Sample
32964-F0
Order no.: 32964-00

First Edition
Revision level: 01/2015
By the staff of Festo Didactic
© Festo Didactic Ltée/Ltd, Quebec, Canada 2001
Internet: www.festo-didactic.com
e-mail: [e-mail]
Printed in Canada
All rights reserved
ISBN 978-2-89289-541-4 (Printed version)
Legal Deposit – Bibliothèque et Archives nationales du Québec, 2001
Legal Deposit – Library and Archives Canada, 2001
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shall also be entitled to use parts of the copyright material as the basis for the production of his/her own
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Both direct and alternatingg current

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Introduction ................................................. V
Courseware Outline
Analog Access to the Telephone Network ....................... VII
Central Office Operation ...................................... IX
Private Automatic Branch Exchange (PABX) ...................... XI
PABX Analog Trunk ........................................ XIII
Digital Trunk .............................................. XV
Sample Exercise Extracted from Analog Access to the Telephone Network
Ex. 2-2 Hybrid Function ...................................... 3
Sample Exercise Extracted from Central Office Operation
Ex. 3-1 Call Processor Functions ............................. 17
Sample Exercise Extracted from Private Automatic Branch Exchange (PABX)
Ex. 1-1 Architecture of a Digital PABX .......................... 31
Sample Exercise Extracted from PABX Analog Trunk
Ex. 1-2 Analog Trunk Interface ............................... 55
Sample Exercise Extracted from Digital Trunk
Ex. 1-2 Digital Trunk Interface ................................ 87
Other Sample Extracted from Analog Access to the Telephone Network
Unit Test ................................................ 117
Instructor Guide Sample Extracted from Analog Access to the Telephone
Network
Unit 1 The Telephone Set ................................. 121
Bibliography
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The Lab-Volt Telephony Training System (TTS), Model 8086, is a powerful learning
tool that allows students to study the operation of modern telephone networks and
digital private automatic branch exchanges (PABX). The TTS is built upon the
Reconfigurable Training Module, Model 9431. This module, which uses state-of-the-
art digital signal processor (DSP) technology, can be programmed to act as different
parts of a telephone network. Interface cards that students install in the training
module allow connection of real analog and digital telephone sets and trunk lines.
A central office (CO) is easily implemented by inserting an analog line interface card
into a training module programmed to act as a central office. Similarly, a digital
PABX is implemented by inserting a digital telephone interface card into a training
module programmed to act as a PABX. Furthermore, simple telephone networks
can be set up quickly by adding analog and digital trunk interface cards to COs and
PABXs implemented with training modules, and interconnecting the modules with
trunk lines. Such telephone networks allow establishment of both intra- and inter-
exchange calls as well as tandem-switched calls.
A Pentium-type host computer, connected to the Reconfigurable Training Module
through a high-speed data link (Ethernet link with TCP/IP protocol), runs the
Lab-Volt Telephony Training System (LVTTS) software. This Windows®-based
software is used to download programs into the DSP memory of the Reconfigurable
Training Module. The LVTTS software is also used to:
• display the functional block diagram of the telephony equipment (CO,
digital PABX, etc.) implemented in the Reconfigurable Training Module,
• change various system settings and options, such as the telephone ringing
cadence, companding type, subscriber names and phone numbers, etc,
• perform step-by-step observation of call routing sequences,
• observe real signals throughout the system in both the time and frequency
domains using modern virtual instruments,
• insert faults in the system (password-protected feature) for troubleshooting
purposes.
The TTS courseware material consists of a series of five student manuals, an
instructor guide for each student manual, and a user guide. The following fields of
telephony are covered in the TTS courseware:
• Analog Access to the Telephone Network
• Central Office Operation
• Private Automatic Branch Exchange (PABX)
• PABX Analog Trunk
• Digital Trunk
Each student manual covers one particular subject and is divided into several units.
Each unit consists of a series of hands-on exercises dealing with certain aspects of
telephony. The exercises contain a clearly stated objective, a discussion, a
summary of the exercise procedure, a detailed exercise procedure, a conclusion,
and a set of review questions. A ten-question test at the end of each unit allows the
instructor to verify the knowledge gained by the student. Each instructor guide
provides the measured results as well as the answers to all questions of each
exercise in the corresponding student manual. It also provides the answers to the
unit test questions. The user guide provides all the information required to set up
and use the Telephony Training System.
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ANALOG ACCESS TO THE TELEPHONE NETWORK
Unit 1 The Telephone Set
Introduction to the public switched telephone network (PSTN). Brief
description of the central office. Familiarization with the functions and
operation of the analog telephone set.
Ex. 1-1 Telephone Ringing
Telephone ringing. AC ringing voltage specifications. The electronic
telephone ringer circuit.
Ex. 1-2 The Telephone Switchhook and Handset
Operation of the telephone switchhook. The handset and speech
circuit. Functions and operation of the speech circuit.
Ex. 1-3 Tone Dialing
Familiarization with DTMF tone dialing. Frequencies used in DTMF
dialing signals.
Ex. 1-4 Pulse Dialing
Familiarization with pulse dialing. Pulse timing. Pulse dialing with
an electronic-type analog telephone set.
Unit 2 The Line Interface
Role of the analog line interface. Block diagram of the analog line interface.
Functions of the analog line interface (BORSCHT functions). Operation of
the analog line interface.

Ex. 2-1 Battery Feed Power Supply
How electrical power is supplied to analog telephone sets.
Subscriber loop interface circuit (SLIC) overcurrent protection.
Equivalent electrical circuit. Maximum resistance (length) of the
telephone line.
Ex. 2-2 Hybrid Function
Balanced transmitted and received signals on the local loop. Role
of the hybrid function in the analog line interface. Implementing the
hybrid function with electronic components.
VII
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ANALOG ACCESS TO THE TELEPHONE NETWORK
Ex. 2-3 Pulse Code Modulation
The coding function. Block diagram of a PCM CODEC. Voice
digitization and recovery. Conversion of the PCM codes to serial
format. Use of companding to improve voice digitization and
recovery.
Ex. 2-4 Companding
Linear quantization and quantization noise. Voice signal-to-
quantization noise (S/N) ratio versus the voice signal level. Using
Q
non-linear quantization to implement companding. Comparing the
S/N ratio versus the voice signal level, with and without
Q
companding.
Ex. 2-5 Time-Division Multiplexing
Why use time-division multiplexing in telephone systems? Time-
division multiplexing of digitized voice signals. The North
American (DS1) and European (E1) multiplexing formats. Time slot
assignment.
Ex. 2-6 Subscriber Signaling
Introduction to subscriber signaling. A typical subscriber signaling
sequence. Telephone ringing. Telephone status (on-hook or
off-hook) supervision. Denying telephone service to a subscriber.
Appendix A List of Equipment Required
Bibliography
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