Panasonic KX-FT25LA Service Manual ▷ View online
4. The unit can copy, but cannot transmit/receive
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KX-FT25LA
5. Unit can copy, but cannot transmit/receive long distance or international communications
The following 2 causes can be considered for this.
Cause 1:
The other party is executing automatic dialling, the call has been received by this unit, and the CED or DIS signal response
time is too long. (In most cases, this unit detects the CNG signal and can respond to the CED or DIS.) (According to the ITU-
T standard, the communication procedure is stopped when there is no response from the other party within 35 sec, so that
the other party releases the line.)
time is too long. (In most cases, this unit detects the CNG signal and can respond to the CED or DIS.) (According to the ITU-
T standard, the communication procedure is stopped when there is no response from the other party within 35 sec, so that
the other party releases the line.)
(Cause and Countermeasure)
As shown in the chart above, the total handshaking time must be reduced. Long distance connection and linking of several
stations means the line connection time cannot be reduced. Accordingly, the following countermeasures should be attempted.
(A) The TEL/FAX DELAYED RING count should be 1. (User parameter: code No. 78)
(B) As the 35 sec. count starts 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.
stations means the line connection time cannot be reduced. Accordingly, the following countermeasures should be attempted.
(A) The TEL/FAX DELAYED RING count should be 1. (User parameter: code No. 78)
(B) As the 35 sec. count starts 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
will be delayed for 2 pauses (about 10 sec.).
Cause 2:
Erroneous detection due to an echo or echo canceler.
(Echo/Echo Canceler)
The signal from FAX1 reaches FAX2 via the 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 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
a possibility that the echo of their own voice will make the call difficult to understand. For this reason, each station (station 1,
station 2) attaches echo cancellers (S1, S2) for international lines or long distance lines. For the echo canceller, the level of the
transmission signal from FAX 1 is compared with the level of the reception signal from FAX2. When the S1 is closed and S2
is open, so that the echo does not return to FAX1.
1(echo). As the distance between station 1 and station 2 is far, the echo returns to FAX 1 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
a possibility that the echo of their own voice will make the call difficult to understand. For this reason, each station (station 1,
station 2) attaches echo cancellers (S1, S2) for international lines or long distance lines. For the echo canceller, the level of the
transmission signal from FAX 1 is compared with the level of the reception signal from FAX2. When the S1 is closed and S2
is open, so that the echo does not return to FAX1.
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KX-FT25LA
(Causes and Countermeasures)
(Cause A)
When a training signal is transmitted from FAX1 during the communication procedure at the time of transmission from FAX1
toFAX2, there is a delay until the echo canceler operates. S1 is closed so that a part of the head of the training signal may
dropout. Normal reception by FAX2 may not be possible, and transmission may not be started.
toFAX2, there is a delay until the echo canceler operates. S1 is closed so that a part of the head of the training signal may
dropout. 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,
7200BPS, 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 affected 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.
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,
7200BPS, 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 affected 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 canceller 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.
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 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 canceller operation stop mode is cancelled by an interval of 250 msec or more.
Reduce receiving sensitivity to reduce the effect of RCV echo signal. (service mode: code No. 598)
mode (code No.593). This is because the echo canceller operation stop mode is cancelled by an interval of 250 msec or more.
Reduce receiving sensitivity to reduce the effect of RCV echo signal. (service mode: code No. 598)
(Cause C)
This model is FAX1 and the other party is FAX2.
For transmission from FAX1 to FAX2, FAX2 executes automatic reception and transmits a CED signal (2100 Hz) followed by
a DIS signal. As the echo cancellers stops as described in cause B, the echo of the DIS signal returns to FAX2. On the other
hand, FAX1 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 FAX1 reach FAX2 one after the other. FAX2 detects an error and communication is not started.
For transmission from FAX1 to FAX2, FAX2 executes automatic reception and transmits a CED signal (2100 Hz) followed by
a DIS signal. As the echo cancellers stops as described in cause B, the echo of the DIS signal returns to FAX2. On the other
hand, FAX1 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 FAX1 reach FAX2 one after the other. FAX2 detects an error and communication is not started.
(Countermeasure C)
When the international DIS detection setting is set in the service mode (code No.594), FAX1 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 first and second DIS signal so that the echo cancellers
operation recovers. An echo is not generated for the second DIS signal.
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 first and second DIS signal so that the echo cancellers
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.
times for trial.
Summary:
Long distance and international communication operation
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KX-FT25LA
6. The unit can copy, but the transmission and reception image is incorrect
(Long distance or international communication operation)
This depends widely on the transmission and reception capability of the other FAX unit and the line conditions.
The countermeasures for this unit are shown below.
The countermeasures for this unit are shown below.
Transmission Operation:
Set the transmitting speed to 4800BPS (service mode: code No. 717) or select the overseas mode.
Reception Operation:
If 80% or more of the reception is incorrect, set the receiving speed to 4800BPS. (Service mode: code No. 718)
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KX-FT25LA
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