Panasonic KX-FP80C, Service Manual

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(Cause and Countermeasure)
As shown in the chart above, the total handshaking time must be reduced, but because of the
long distance connection and linking of several stations, the line connection time cannot be
reduced. Accordingly, the following countermeasures should be tried.
(A)... As the 35 sec. count is started directly after dialing or directly after the START button has
been pressed for models with a START button, the other party should be called manually, if
possible. Another possibility is entering two pauses at the end of the auto dial number on the
transmission side. Then the count start time can be delayed for 2 pauses (about 10 sec.).
Cause 2:
Erroneous detection because of an echo or an echo canceler.
(Echo/Echo Canceler)
The signal from FAX1 reaches FAX2 via stations 1 and 2, but the reflection signal at station 2 also
returns via station 1 (echo). As the distance between station 1 and station 2 is far, the echo
returns to FAX 1 at a max of 600 msec after transmission. There is a possibility that this signal is
detected erroneously as the signal from FAX2. For a normal call, there is also a possibility that
the echo of their own voice will make the call difficult to understand. For this reason, each station
(station 1 and station 2) attaches echo cancelers (S1 and S2) for international lines or long
distance lines. For the echo canceler, the level of the transmission signal from FAX 1 is compared
with the level of the reception signal from FAX2. When the transmission signal is larger, S1 is
closed while S2 is opened when it is smaller. In other words, for transmission from FAX1, S1 is
closed and S2 is open, so that the echo does not return to FAX1.
(Causes and Countermeasures)
(Cause A)
When a training signal is transmitted from FAX1 during the communication procedure at the time
of transmission from FAX1 to FAX2, there is a delay until the echo canceler operates. S1 is closed
so that a part of the head of the training signal may drop out. Normal reception by FAX2 may not
be possible, and transmission may not be started.
(Countermeasure A)
When the international line mode is ON in the service mode (code No. 521), a dummy signal is
attached to the head of the training signal to prevent this problem. As this is normally ON, it is
necessary to reconfirm that this has not become OFF. When the international mode is switched
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