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(2) Countermeasures on Transmitter
Ignore the first DIS from the called party and respond to the second DIS.
By ignoring the first DIS, a no-signal state lasting for 0.1 sec or more can
be created on the telephone line.
This turns the echo suppressor back on, and echo is not generated from
then on.
1st DIS is
ignored.
Preamble
Fig. A-34 Echo Countermeasure on Transmitter
(3) Countermeasures on both transmitter and receiver
After transmitting binary signals, ignore the binary signals from the other
party for 0.6 to 0.7 sec. (This function is provided on all Canon facsimi-
les.)
After transmitting each binary signal, ignore binary signals from the other
party for 0.6 to 0.7 sec (differs according to model of facsimile) as shown
in the Fig. A-35.
This is because the regular echo delay is within 0.6 sec. By performing this
process, the facsimile is not likely to be deceived by its own signals.
Moreover, since the preamble time is 1.0 sec, a preamble of 0.3 to 0.4 sec
can be received even in the case of domestic communications with a short
propagation delay. This countermeasure does not cause any problems.
Long distance
transmission line
TX
RX
CED
Preamble
DIS
Preamble
DIS
DCS
No-signal state of
0.1 sec. or more
A–33
1
2
3
4
5
6
A
çi
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