LESSON 3
ECHO SUPPRESSORS AND COMPANDORS
SCOPE ............................. Echo suppression in long-lines transmission;
use of compandors to minimize level variation
and improve signal-to-noise ratio.
CREDIT HOURS ...................... 2
TEXT ASSIGNMENT ................... Attached memorandum, para 3-1
thru
3-4;
Appendix C, pages C-1 thru C-17
MATERIALS REQUIRED................ None
SUGGESTIONS ....................... Follow the study guide below.
LESSON OBJECTIVES
When you have completed this lesson, you should:
1.
Know that the purpose of a compandor is to improve the signal-to-noise
ratio for voice communication.
2.
Know that a compandor amplifies weak and strong signals unequally.
3.
Know that a compandor limits the variation in signal levels on the line.
4.
Know that the presence of compandors and echo
suppressors
may
be
detrimental to data transmission over a telephone network.
5.
Know that an echo suppressor controls the transmission path in a telephone
network.
6.
Know that unbalanced hybrid coil circuits may cause echoes in long-
distance voice communication circuits.
7.
Know that a hybrid coil circuit is necessary to convert two-wire to four-
wire operation.
8.
Be able to calculate signal levels passing through a hybrid coil circuit.
STUDY GUIDE
1.
SOUND INTENSITY
Several arbitrary scales are used to describe sound levels in the
electronic sciences.
One type is used in Appendix C.
The volume of sound
(level) in this scale is based on the average threshold of hearing. The scale
used identifies the threshold of hearing level as -60 db.
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