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Telephony 101
I S D N L ATA P O T S D L C L E C 8 AT M I S D N L ATA P O T S D L C L E C AT M I S D N L ATA P O T S D L C L E C AT M I S D N L ATA
Telephony 101
A Basic Introduction to How Telephone Services
Are Delivered in North America
The much touted convergence of a range of key communications industries
cable TV, computers, local and long distance telephone service providers, among
othershas added myriad new players to the market for telephony services.
And, of course, in the thriving telecommunications market, new individuals are
joining both established and new telephony companies every day.
While the stunning simplicity of the interface to the public switched network
the telephonelargely masks the complexity of the technology from the general
public, the public network is, after all, the most massive and sophisticated net-
working system ever created. New entrants to the telephony business have an
obvious need for a thumbnail introduction to a set of technologies and services
that at first can seem daunting in their reach and complexity.
Telephony 101 is intended to begin filling this need by providing a basic under-
standing of how telephone services are currently delivered in North America.
First, it provides a concise overview of the
impressive list of revenue-producing ser-
vices that make the market so inviting to
begin with. It then provides a basic look at
the access, switching, and transmission
infrastructures that are used to deliver
these services. Finally, it profiles the key
business and service organizations that
todays telephony subscribers expect to
interface and use when they do business
with a telephony provider.
Much of North Americas telecommunications infrastructure was designed and
built by Northern Telecom. We deployed the first fully digital switches almost
two decades ago, and we have teamed with network providers worldwide to deliv-
er over 110 million lines of digital switching in over 90 countries. Our SONET
and microwave radio transmission product line is the benchmark against which
state-of-the-art is measured, with over 10 million DS-1 lines of SONET and two
million DS-1 lines of microwave capacity installed. We have helped build net-
Telephony 101
I S D N L ATA P O T S D L C L E C 8 AT M I S D N L ATA P O T S D L C L E C AT M I S D N L ATA P O T S D L C L E C AT M I S D N L ATA
Introduction
This book provides your basic
introduction to telephony. But
no beginning course has ever
provided all the answers.
We'd be glad to help in the future.
If you have further questions
about telephony services
or technologies, please
feel free to call us at
1-800-NORTHERN.
Draw on Our Experience works for everyone from the largest Bell Operating Company, to the worlds
largest corporations, to the smallest independent telephone service provider.
These experiences have given us an understanding of telephony issues from the
perspectives of both the established provider and the new entrant to the market.
We hope Telephony 101 translates this broad experience into a short and useful
introduction to services and technologies that drive the telephony market.
I n t r o d u c t i o n Telephony 101
I n t r o d u c t i o n
TABLE OF CONTENTS
The Opportunity: Revenue-Producing Telephony Services. . . . . . 1
Standard Business and Residential Service
. . . . . . . . . . . .
1
Plain Old Telephone Service (POTS)
2
Custom Calling Features
3
CLASS Features
4
Voice Mail
7
Non-Switched Transport Services
7
Advanced Voice and Data Services
. . . . . . . . . . . . . . .
8
Centrex Business Services
9
Call-Center Services
15
Advanced Display-Based Features
17
Voice-Activated Services
19
Integrated Services Digital Network (ISDN)
20
Switched 56 Data Service
22
Multi-Rate ISDN/Dialable Wideband Service and Other
Bandwidth-on-Demand Services
23
Frame Relay Service
26
Long Distance Services
. . . . . . . . . . . . . . . . . . . .
28
Information Database Services
29
Enterprise Network Services
29
Data and Video Services
30
Multiple Dialing Plans
30
Operator Services
. . . . . . . . . . . . . . . . . . . . . .
31
Traditional Services
31
Value-Added Service Opportunities in the Operator Services Market
33
Non-Traditional Operator Services
34
The Technology of Telephony . . . . . . . . . . . . . . . 37 Overview of the Public Network
. . . . . . . . . . . . . . . .
3 7
The Network Building Blocks
37
Organization of the Network
37
The Historical Network Hierarchy
39
Types of Carriers
40
The Importance of LATAs
43
POPs and Access Charges/Interconnection Fees
44
Equal Access
45
Numbering Plans
45
Key Concepts in Telephony Switching
. . . . . . . . . . . . . .
47
Electromechanical and Analog Switches
47
The Move to Digital Switching
48
How Digital Technology Works
49 Key Components of the Digital Switch
. . . . . . . . . . . .
51
Call Processing
52
Planning and Engineering the Digital Switch
57
Digital Switch Maintenance
58
Environmental and Powering Concerns
58
ATM in the Switched Network
59
Key Concepts in Telephony Transmission
. . . . . . . . . .
60
Analog Transmission
60
Digital Transmission
61
Transmission Media
61
Transmission Rates
63
Interoffice Signaling Protocols and Trunks
66
Key Concepts in Telephony Access
. . . . . . . . . . . . .
68
Line Access
68
Trunk Access
71
Wireless and Cellular Access
71
Fiber-Optic Access
71 Advanced Intelligent Networking
. . . . . . . . . . . . . .
72
Sample AIN Call
74
Key AIN Network Elements
75
Reliability and Survivability in the
Public Switched Network
. . . . . . . . . . . . . . . . .
75
Reliability in Switching Components
75
Reliability in the Transmission Network
76
The Business of Telephony . . . . . . . . . . . . . . 79
Marketing Telephone Services
. . . . . . . . . . . . . . .
79
POTS Services
79
IntraLATA Toll
80
InterLATA Toll
80
Advanced Services
80
Cooperative Marketing
81
Telephone Operations
. . . . . . . . . . . . . . . . . .
82
Network Planning and Engineering
82
Business Office and Trouble Desk
82
Billing
84
Other Tablestakes Public Network Services
84
A Glossary of Key Telephony Terms . . . . . . . . . . . 87
I n t r o d u c t i o n The success of a telephony provider is inevitably influenced by how it positions
the suite of features that will be at the core of its service offering. On the one
hand, few players are likely to be successful if their service portfolio isnt per-
ceived as at least as good as the one customers currently have to choose from.
On the other hand, few providers are likely to attract and keep subscribers if they
cant deliver at least some key services that make their offering stand out from the
competition.
This section details the wide range of revenue-producing features and services
that todays providers are delivering from state-of-the art digital switching
systems.
There are a set of standard services that can be offered by most modern digital
switching systems. These standard servicesthe way they operate, the terminals
and telephones they require, and their interworking with other switching
systemsare defined in the United States and Canada by Bell Communications
Research (Bellcore), Stentor, and a key group of standards bodies.
Standardization means that subscribers can normally obtain these services no
matter where they live, and choose from many different vendors with the
confidence that any standard terminal will work with the service.
1
Telephony 101
I S D N L ATA P O T S D L C L E C 8 AT M I S D N L ATA P O T S D L C L E C AT M I S D N L ATA P O T S D L C L E C AT M I S D N L ATA
STANDARD BUSINESS AND RESIDENTIAL SERVICES
1
The Opportunity: Revenue-
Producing Telephony Services
Plain Old Telephone Service (POTS)
Custom Calling Features
Advanced Calling Features,
such as Caller ID
Advanced Services for
Display-Based Telephone Sets (ADSI)
Residential Services
Digital Voice and Data
on One Line (ISDN)
Voice-Activated Services
Operator Services
Voice Mail
ISDN Line-Level Interface (BRI)
ISDN High-Bandwidth
Trunk Interface (PRI)
Centrex Business Telephone Groups
Automatic Call Distribution (ACD)
Business Services
Frame Relay Data Transmission
Videoconferencing (Switched 56)
Dialable Wideband Services/
Bandwidth on Demand
Toll Calls
Wide-Area Business Networks
Virtual Access to Private Networks
Calling Card Services
Long-Distance Services
Voice-Activated Services
Dedicated Long-Distance Lines
ISDN Primary Rate Interface (PRI)
Packet Data Transmission Service
Frame Relay Data Transmission Service
Dialable Wideband Services
Toll and Assistance
Intercept Services
Directory Assistance Services
Alternate Billing
Operator Services
Custom Information and Listing Services
Figure 1-