Oki B4100 - Manual (Page 306)

40055101TH Rev.4 306 /
7.2.15 Tone (TEL/FAX) Send Test
Start
No
Pseudo-Ring Back Tone
signal appears
across L1 and L2?
Yes
MF signal appears across CN6-A8, B8
(S) and CN6-A12, B12 (0V) of MCNT board?
Replace MCNT Board.
Replace NCU Board.
Solved?
Replace MCNT Board.
Signal route:
CN3-15, 16
→
T1-3, 1
→
CN1-3, 4
End
No
Yes
Yes
No
Return to section 7.2.1
Connect oscilloscope probe
across the line terminals
L1 and L2.
Perform TONE (TEL/FAX)
SEND TEST. (See 6.12.)
Possible cause:
CML signal
Signal route:
IC12-7
→
IC29-13
→
IC29-3
→
IC30-1
→
CN6-A8, B8 (S)
Note: The pseudo-ring back tone is sent to the
telephone line for TEL/FAX automatic
switching.