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GD-1220/1221 © 2006 - 2008 TOSHIBA TEC CORPORATION All rights reserved
ELECTRICAL CIRCUITS
4 - 10
4.2.5 CI detection circuit
NA/TW models
Fig. 4-10
The CI detection circuit consists of the photocoupler (PC2), ASIC (IC23) on the MAIN board and the
other peripheral devices to detect a ring signal input from the telephone line.
The ASIC makes the CML1 signal become LOW to connect the CI detection circuit to the telephone
line.
When a ring signal is input from the telephone line, the photocoupler is repeatedly turned ON/OFF. This
allows the CI1 signal to become a pulse signal and input to the ASIC on the MAIN board, thereby
detecting the ring signal.
Signal Name Type Active Description Destination
CI1 I - Line 1 CI Detect Signal IC23
CN10
Lb
La
0
1
0
1
+12V
RLY2
CML relay
CML1
Q51
3
4
3
327
6517
CI1
17
SG
AG
5VPS
R79
CN9
CN262
PC2
ZD3ZD1 C1 R2
D52
IC23
ASIC
CN5
CN5
27
65
144
162
NCU board
Line
FAX board MAIN board
112
9
10
43
1
2
4
3