telecommunications training, dvd video courses, online telecom course, IP networking and MPLS training, VoIP fundamentals, books, certification

Teracom Tutorial: Voice Digitization (1)

Go to Teracom home page scheduled public seminars, instructor-led telecom training, networking training, telecommunications training, VoIP training, MPLS training courses self-paced DVD video courses telecom, datacom, networking, IP, MPLS, wireless, training, learning, courses, online online certification and testing info on bringing any Teracom seminar to your location for a private team training session telecommunications training book, networking book Free online tutorials, lessons, articles and more!
site map
Register for Certification
Register: Online Courses
Register for a Seminar
Order DVDs
Order Books
Certification Exams
Online Course Previews
Video Previews
CPE Credits
free bonuses - certification and online courses
Online Courses
Instructor-Led Courses
Private Onsite Training
DVD-Video Courses
Reference Books
Free Tutorials
Why take our courses
Who will benefit
Value pricing
About Teracom
Contact us
Policies and FAQs
be notified of new tutorials, seminars, video releases and more
Teracom Tutorial: Voice Digitization (1)
4.09  Voice Digitization - Part 1
Change from continuous in value to discrete in value
Change from continuous in time to discrete in time
Code value of sample into 1s and 0s

We look in detail at the voice digitization process to derive the data rate - number of bits per second - required to communicate a digitized voice signal. There are many systems deployed which operate at these rates. Since they are digital systems, we can use them to communicate data, even though they were designed originally for voice.

There are three steps in voice digitization: quantization, sampling and coding.
Quantization is the process of changing from a signal which is continuous in value to a signal which is discrete in value. This is accomplished by dividing the possible range of values into a number of “bins” or levels or steps, and assigning a number to each of these levels. Then, when asked what the value of the signal is, we say that the signal is “in level #42” rather than measuring its voltage. Another example of quantization is sugar cubes. Instead of putting some fractional value of a bag of sugar in your coffee, your choice is “one lump or two”. The sugar has been quantized into uniform lumps.
The second step is sampling. Sampling is the process of changing the signal from being continuous in time to one that is discrete in time. On a regular basis, we take the value of the signal and record it. The value of the signal is the level number. How often do we need to sample the signal? A mathematician by the name of Nyquist proved that the signal has to be sampled more than twice as often as the highest frequency bandwidth of the signal to be able to reproduce it. This is called the Nyquist Rule.
The third step is coding. The value of the signal taken at each sample (the level number) must be coded into 1's and 0's so that it can be transmitted over a digital carrier system or stored in a computer.
The objective of this process is to take the codes representing the value of each sample and transmit them to the far end. At the far end, we perform the reverse process: re-creating the analog waveform from the received codes by de-coding the level number, generating a voltage with a value equal to that of the center of the level, and smoothly changing the voltage in this manner as each new code comes down the line.
The whole point in doing this is to move the analog voice signal from the near-end loop to the far-end loop without adding in any noise.
There is in fact a small amount of noise added in, up front, as part of the analog-to-digital conversion. This is the quantization error, the difference in value between the center of the level, and where the signal actually was.
How do we make the quantization error smaller on average? Make the levels finer. How many levels does the telephone company use? Enough so that a human can't hear the quantization error noise on the line.
Source: Teracom Course 101, Telecom, Datacom and Networking for Non-Engineers,
Module 1: Fundamentals of Telecommunications, slide 4.09
online telecom training courses
online courses
telecommunications certification
instructor-led course 101: telecom, datacom and networking for non-engineering professionals
textbooks, reference books, certification study guides
DVD video courses
DVD-video courses
boot camp
mind the gap!
tell a friend:
Join our satisfied customers including:
at&t verizon bell canada microsoft intel cisco gsa cox cable
Copyright © Teracom Training Institute.   All rights reserved.    privacy policy    contact us    FAQs, help and policies