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3. NCU BOARD
"NCU board" is an abbreviation for Network Control Unit board. This
board is located at the telephone line - facsimile interface. This board func-
tions to detect signals arriving from the telephone line to transfer them to
the MODEM on the SCNT board, and to switch the line between the fac-
simile and telephone.
The main functions of the NCU board are as follows:
Exchange
Fig. 6-3 Location of NCU Board
• Off-hook detection
• Formation of DC loop
• Detection of calling identification (CI)
• Line signal monitor
• Dial control
• 2-wire/4-wire conversion
• Protective circuits
• Telephone connection control
T11
T12
T21
NCU board
T22
L1
L2
Facsimile
FACSIMILE SYSTEM
1
2
3
4
5
MODEM
6
SCNT board
ït
çi
6–5
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