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3.3
Detection of Calling Identification (CI)
The CI detection function detects the calling identification (CI) sent from
the exchange. Normally, when dialing is performed from the calling party,
the bell of the telephone on the incoming call side rings according to the CI
from the exchange.
The CI detection function is required for automatic reception by a facsim-
ile. When CI is detected, the facsimile automatically receives the docu-
ment.
The DC component of the CI arriving from the telephone line is cut by a
capacitor (C1). The signal is then half-rectified by two photocouplers, PC1
and PC2, respectively, and the waveform is shaped by IC1 and IC2. The
waveforms of each of these outputs (CI1 and CI2) are aligned by OR cir-
cuit IC3, and the resulting waveform is sent to the system controller on the
SCNT board as CIOR together with CI1 and CI2.
The system controller distinguishes that the signal is CI by the waveform
pattern of the arriving signal.
Off-hook
T1
detection circuit
T2
L1
CML relay
L2
Fig. 6-8 CI Detection Circuit
C1
PC1
PC2
To 2-wire/4-wire conversion circuit
FACSIMILE SYSTEM
1
2
3
4
5
6
CI2
IC1
CIOR
IC3
CI1
ït
IC2
çi
NCU board
6–9
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