Toshiba ESTUDIO170F, Service Manual

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e-STUDIO170F Circuit Description January 2005 © TOSHIBA TEC
7 - 62
7.4.4 CI Detect Circuit
US/CA models, SG/HK models
Fig.7-44
The CI detect circuit consists of the photo-coupler (PC2), ASIC (I/O port: IC38) on the Main PBA, and
other peripheral devices to detect a ring signal input from the telephone line.
The ASIC causes the CML signal to go LOW to connect the CI detection circuit to the telephone line.
When a ring signal is input from the telephone line, the photo-coupler repeats turning on and off. This
allows the CISX signal to be a pulse signal and input to the ASIC on the Main PBA, thereby detecting
the ring signal.
Signal Name Type Active Description Destination
CISX I - CI detect signal ASIC
CN10
Lb
La
Line
0
1
0
1
+12V
RLY2
CML relay
CML
Q51
3
4
3
3 49
35 17
NCU PBA Main PBA
IC38
ASIC
(I/O port)
CISX
17
SG
AG
+5VPS
R79
CN9
CN16
PC2
ZD3 ZD1 C1 R2
D52
3
10
12
4
3 2
1
4
9
1