CONTENTS
ix
4.4
Essential Concepts in Transmission
75
4.4.1
Introduction
75
4.4.2
Two-Wire and Four-Wire Transmission
75
4.5
Introduction to Multiplexing
78
4.5.1
Definition
78
4.5.2
Frequency Division Multiplex
79
4.5.3
Pilot Tones
84
4.5.4
Comments on the Employment and
Disadvantages of FDM Systems
85
Review Exercises
85
References
87
Chapter 5
Transmission Aspects of Voice Telephony
89
5.1
Chapter Objective
89
5.2
Definition of the Voice Channel
90
5.2.1
The Human Voice
90
5.3
Operation of the Telephone Subset
91
5.3.1
The Subset Mouthpiece or Transmitter
93
5.3.2
The Subset Earpiece or Receiver
93
5.4
Subscriber Loop Design
93
5.4.1
Basic Design Considerations
93
5.4.2
Subscriber Loop Length Limits
94
5.4.3
Designing a Subscriber Loop
95
5.4.4
Extending the Subscriber Loop
97
5.4.5
"Cookbook" Design Methods for Subscriber
Loops
98
5.4.6
Present North American Loop Design Rules
101
5.5
Design of Local Area Wire-Pair Trunks (Junctions)
102
5.5.1
Introduction
102
5.5.2
Inductive Loading of Wire-Pair Trunks
(Junctions)
102
5.5.3
Local Trunk (Junction) Design Considerations
103
5.6
VF Repeaters (Amplifiers)
103
Review Exercises
104
References
105
Chapter 6
Digital Networks
107
6.1
Introduction to Digital Transmission
107
6.1.1
Two Different PCM Standards
108
6.2
Basis of Pulse Code Modulation
108
6.2.1
Sampling
108
6.2.2
Quantization
109
6.2.3
Coding
113
6.3
PCM System Operation
118
6.4
Line Code
119
6.5
Signal-to-Gaussian-Noise Ratio on PCM Repeatered
Lines
120