Panasonic KX-F900 Service Manual page 38

L
KX-F900
@ Unit can copy, but can not transmit/receive long distance or international communication
The following 2 causes can be considered for this.
Cause 1:
The other party is executing automatic calling, the call has been received by this unit, and this time until response with a CED
or DIS signal has been too long. (In almost case, this unit detects CNG signal and can respond to CED or DIS.) (According to
the ITU-T standard, the communication procedure is stopped when there is no response from the other party within 35sec, so
that the other party releases the line.)
(Time until Response)
Line Connection
Time
l
Ringing Time
(about 4 sec/ring)
Other party FAX
machine dials
False ring
i--1 I---1
- .____FaIcslel _1ngeSic?d T 1_ e
(about 17 sec depending on the
setting user program mode #30)
Max 35 sec
3 sec I sec
sCEn_ Signal _sD_St .gnal
75 msec
Other party
FAX machine
detects the
DIS signal.
(Cause and Countermeasure)
As shown in the above chart, the total handshaking time must be reduced, but because of the long distance connection and
linking of several stations, the line connection time can not be reduced. Accordingly, the following countermeasures should
be tried.
(A) The TEL/FAX DELAYED RING count should be 1. (user parameter: code No. 06)
(B) As the count of 35 sec 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 entry of two pauses at the end of the auto dial number of the transmission side, In this way, the start
time for the count can be delayed by 2 pauses (about 10sec).
Cause 2:
Erroneous detection because of echo or erroneous detection because of an echo canceler.
FAX 1 j /o-J _ FAX 2
_ Station 1 Sl
t
S2 iStation 2
I S I i
i
s
2 Line Type
The sea bottom cable or satellite
communication path. (4 Line Type)
2 Line Type
(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 long, the echo returns to FAX 1 max. 600msec after transmission,
so than there is the possibility that this signal is detected erroneously as the signal from FAX2 and that trouble is caused. In
the case of a normal call, there is also the possibility that the echo of the own voice will make the call difficult to understand.
For this reason, each station (station 1, station 2) attaches echo cancelers ($1, $2) in case of international lines or long dis-
tance lines. For the echo canceler, the level of the transmission signal from FAX 1 is compared with the level of the reception
signal from the FAX2, and when transmission signal is larger, $1 is closed, while $2 is opened when it is smaller. In other
words, with transmission from FAX1, $1 is closed and $2 is open, so that the echo does not return to FAX1.
-38-