Panasonic KX-FM330GR Service Manual page 93

(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 normally is ON, it is necessary to reconfirm that this has not become OFF. When
the international mode is switched OFF, the transmission side will try the training signal three times at each speed (9600BPS,
4800BPS and 2400BPS). If NG, it will drop the speed by one rank (fall-back). When the international mode is switched ON,
each speed will be tried only twice. In other words, the slower speed with fewer errors can be accessed more easily. This is
done because the line conditions may deteriorate and the picture may be disturbed more easily during communication for
international lines or long distance communication, even when the training is OK. The default value is ON as preference is given
to clearer pictures rather than speed.
(Cause B)
The echo canceler operation is stopped with a 2100Hz signal. (i.e. S1 and S2 become ON).Accordingly, when FAX1 has
executed automatic reception, a CED signal is output. If this signal is 2100Hz, S1 and S2 will become ON. Then the echo of
the DIS signal output afterwards may be received and FAX1 may execute an erroneous operation, preventing communication
from starting.
(Countermeasure B)
In the service mode, the CED signal frequency is set to 1100 Hz (code No.520), or the time setting between the CED signal and
the DIS signal is set from 75 msec to 500 msec in the service mode (code No.593). This is because the echo canceler operation
stop mode is canceled by an interval of 250 msec or more.
Reduce receiving sensitivity to reduce the effect to RVC echo signal. (Service mode: No.598)
(Cause C)
This model is FAX1 and the other party is FAX2.For transmission from this model to FAX2, FAX2 executes automatic reception
and transmits a CED signal (2100 Hz) followed by a DIS signal. As the echo cancelers stops as described in cause B, the echo
of the DIS signal returns to FAX2. On the other hand, this model detects the DIS signal and transmits a DCS signal. In other
words, it is possible that the echo of the DIS signal and the DCS signal transmitted from this model reach FAX2 one after the
other. FAX2 defect an error and communication is not started.
(Countermeasure C)
When the international DIS detection setting is set in the service mode (code No.594), this model does not respond to the first
DIS signal and returns a DCS signal only for the second DIS signal.In other words, there is an interval of 250 msec between
transmission of the first and second DIS signal so that the echo cancelers operation recovers. An echo is not generated for the
second DIS signal.
Note:
When the other FAX does not respond with a DCS signal after DIS signal transmission, the DIS signal is transmitted three
times for trial.
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KX-FP320G / KX-FM330G