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89

Fig. a 

(Overlapping the Echo of the DIS signal and DCS signal)

Fig. b 

(Countermeasure by Changing the CED Frequency)

No. Countermeasure Side

Echo Communication Problem Example

Countermeasure

Service Code

1

Sending side

Some time is needed to compare the level 
of the receiving and sending signals for the 
echo canceler. The header of the training 
signal lacks due to a switching delay to 
close S1.

Add a dummy signal to the beginning of 
the training signal.

Service code (521)
(International mode select)
This countermeasure becomes 
the default value.

2

Receiving side

The echo canceler function stops according 
to a CED signal frequency of 2100Hz (S1 
and S2 are both ON), a DIS signal is 
returned as an echo, and a DCS signal 
from the sending side overlaps the DIS 
echo. Then the receiving side FAX cannot 
retrieve the DCS signal.
(Refer to Fig. a)

Change to a 1100Hz CED signal fre-
quency. (Refer to Fig. b)

Service code (520)
 (CED frequency select)

Receiving side

Change the regular rime of 75 msec 
between the CED signal and DIS signal 
to 500 msec. This will give at least 250 
msec to recover the echo canceler 
operation. (Refer to Fig. c)

Service code (593)
 (Time between CED and 300 
bps)

Sending side

The sending side FAX sends a DCS 
signal not after receiving the 1st DIS 
signal but after receiving the 2nd DIS 
signal. (Refer to Fig. d) 

Service code (594)
 (Overseas DIS detection 
select)

3

Sending side

Communication failure occurs in a long dis-
tance communication on the telephone line 
without an echo canceler.

or

There are some cases (e.g. Mobil comms.) 
which cause the collision of TX / RX signals 
due to the delay / echo and noise of the 
network / terminal. (Refer to Fig. e)

Decrease the transmission level from -
9 dBm to -15 dBm and the echo level 
will decrease.

Service code (596)
 (Transmit level set)

4

Sending side
Receiving side

Decrease the receiving sensitivity from 
-13 dBm to about -32 dBm so an echo 
signal will not received.

Service code (598)
 (Receiving sensitivity)

5

Sending side
Receiving side

Set additional Pause time (Service 
mode: code No. 774) in between the 
original and its repeated signals, to pre-
vent the collision of the signals at both 
end.

Service code (774)
 (T4 timer)

90

Fig. c 

(Countermeasure by Changing the Interval Between CED and DIS)

Fig. d 

(Countermeasure by Ignoring the 1st DIS)

(Fig. e)

(Long distance or international communication operation)

This symptom highly depends on the transmission and reception capability of the other FAX unit and the line conditions.
The countermeasures for this unit are shown below.

Set the transmitting speed to 4800BPS (service mode: code No. 717) or select the overseas mode.

If 80% or more of the reception is incorrect, set the receiving speed to 4800BPS. (Service mode: code No. 718)

• Refer to Service Function Table (P.59).

<TX side signal>

<RX side signal>

<Countermeasure>

2nd / 3rd DCS / Training

& delayed CFR / FTT

at TX side

2nd / 3rd EOP / EOM / MPS

& delayed MCF / PIP / PIN / RTP / RTN

at TX side

delayed DCS

& 2nd / 3rd / --- DIS

at RX side

91

Recording FAX signal is one of the useful analysis measures to solve communication problems.
The way of recording easily by using PC is shown as follows.

• 1 jig
• 1 PC (with LINE IN)
• 1 audio cord (mini jack supported)
• 2 tel cords

FAX SIGNAL RECORDING JIG

1. Set LINE IN to be valid in the volume control setting.

Refer to the PC instruction book.

2. Start up the PC software “SOUND RECORDER”. (This software is bundled to Windows OS, which can create WAV file.)

Set the audio format “PCM 22.050kHz, 8bit, mono”.

3. Click the record button and start recording after acquisition the signal.

•  Not to be wind wave patterns on the wave monitor.
• Please compress the recording data when you send attaching to E-Mail because the data size will be so heavy.
• Any software which can create WAV files is available.

PQJJ1T004Z

JACK1, JACK2

2

PQJJ1D010Z

PIN JACK

1

ECQE2155KF
 or
ECQE2E155KC

CAPACITOR

2

MA4020

DIODE

2

92

If, after the call is connected, the customer describes the situation and it is determined that the problem can be corrected by
making parameter changes, this function makes it possible to change parameters such as the user code and service code from
another fax (using DTMF tones). Therefore, travel to the customer's location is not required. However, it is not possible to
change all the parameters remotely (Program Mode Table (P.93)). The function used to accomplish this is remote program-
ming.

First, in order to check the current status of the service code parameter, print out the setup list (code: 991) and the service list
(code: 999) from the customer's fax machine.
Based on this, the parameters for the desired codes can be changed.
The procedure for changing and listing parameters is described on Entering the Remote Programming Mode and Changing
Service Codes (P.92). Also, before exiting the remote programming mode, it is advisable to obtain a new list to confirm that the
changes were made correctly.

Since the connected telephone is in use during the remote programming mode, it may be helpful to ask the customer to switch
to the speakerphone. This frees the customer from the need to remain right next to the fax while you are making parameter set-
tings. When finished, inform the customer. Also note that in very noisy locations where the DTMF tones are not audible, the
remote programming function will not work.

(*1): Program Mode Table (P.93)