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FACSIMILE SYSTEM
7. G4CNT BOARD
The G4CNT board is provided on G4 facsimiles, and is the equivalent to
the NCU board on a G3 facsimile. The G4CNT board performs connection
with the ISDN line to perform digital communications. In the case of a G4
facsimile, G4 communications is performed. In the case of a G3 facsimile,
digital signals are converted to analog signals at reception and analog sig-
nals are converted to digital signals at transmission by the PCM
and MODEM on the G4CNT board to perform G3 communications.
•
CPU
The G4CNT board comprises the following ICs.
As the block diagram below shows an example where two lines can be
used simultaneously, two MODEMs are provided.
The G4CNT board has a CPU (V821) for controlling the entire G4CNT
and a slave CPU (V853). The slave CPU performs coding (MR, MMR or
JBIG) on the MR data stored in DRAM matched to the functions of the
machine at the other party, and during reception codes the coded data from
the other party to MR data for storing on DRAM.
• ISDN interface
As its name implies, this interfaces the facsimile with the ISDN line, and
performs outgoing/incoming call control and layer 1 control (extraction of
data and synchronization).
• HDLC controller
This controller converts data to HDLC format and performs serial/parallel
conversion to enable detection of data errors.
• SLIC
This functions as an
the facsimile. For this reason, it forms the DC loop with the analog tele-
phone and detects the off-hook state of the telephone.
• Dual port RAM
This RAM is for separating the V821CPU and V853 slave CPU systems.
6–32
exchange
when an analog telephone is connected to
CODEC
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