Panasonic KX-F1200 Service Manual And Technical Manual page 59

[ KX-F1200
_Gau_u and (Joulu[urmua_uru)
(Cause A)
When the training signal is transmitted iro_k i AXi c_unngtn_ _u_,._,u_J_caUo_ p_u_udu_ at the tlt_u ui traa_mJssion from
FAX1 to FAX2, there is a delay until the echo canceler operates and Sl 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 becomes ON 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 becomes 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), and in case of 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 are reached
more easily. This is done as the line conditions may deteriorate and the picture may be disturbed more easily during commu-
nication in case of international lines or long distance communication, even when the training has been 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 signal of 2100Hz (i.e. Sl and S2 become ON).
Accordingly, when FAX1 has executed automatic reception, a CED signal is output, and if this signal should be 2100Hz, $1
and $2 will become ON. Then the echo of the DIS signal output afterwards may be received and FAX1 may execute errone-
ous operation, preventing start of communication.
(Countermeasure B)
In 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 75msec to 500msec in service mode (code No.593). This is done because the echo canceler op-
eration stop mode is cancelled with an interval of 250msec or more.
(Cause C)
KX-F1200 shall be assumed for FAX1 and a set of a different company shall be assumed for FAX2.
In case of transmission from the KX-F1200 to FAX2, FAX2 executes automatic reception and transmits a CED signal (2100
Hz), followed by a DIS signal. As here the echo cancelers stops as described in cause B, the echo of the DIS signal returns
to FAX2. On the other hand, the KX-F1200 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 the KX-F1200 reach FAX2 one after the other, FAX2 ex-
ecutes erroneous detection, and communication are not started.
(Countermeasure C)
When international DIS detection setting is made effective in service mode (code No.594), the KX-F1200 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 250msec between transmission of the first and the second DIS signal, so that the echo
cancelers operation recovers and no echo is 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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