Canon fax basic 2000 서비스 매뉴얼

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7.2

Unusual Factors

(1) Impulse noise

“Impulse noise” is the irregular noise that occurs because of the contact

points at an exchange.

This noise is easily generated by step-by-step exchange that operate by

mechanical contacts.

Impulse noise is no problem in telephone conversations, except that it can

be a little offensive to the human ear when it occurs. In G3 facsimile trans-

mission, however, the same image defects that occur with white noise and

level variation occur.

Fig. A-25   Impulse Noise Caused by a Step-By-Step Exchange

(2) Short breaks

A “short break” is a sudden drop in the reception signal level of 6 dB or

more for 1 msec to 60 sec continuous. Short breaks are caused by fading in

microwave radio ralay and satellite communications system zones or by

faulty contacts on equipment and cables.

Short breaks do not cause any special problems in telephone conversations

as long as the break is not continuous. However, in G3 facsimile transmis-

sion, the same phenomenon as in level variation and impulse noise occur

significantly.

Fig. A-26   Short Break Area

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100mV

Time (msec.)

10

6

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0

Le

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e

l

drop

(dB)

Impulse noise

or

level variation

Short break

Level variation

Line trouble

or

level variation

Continuous time

1ms

2ms

60s

120s