Toshiba ESTUDIO170F, Service Manual

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e-STUDIO170F Circuit Description January 2005 © TOSHIBA TEC
7 - 60
EU/AU models
Fig.7-42
The line current detect circuit consists of the line current detection IC (IC2), ASIC (I/O port: IC38) on the
Main PBA, and other peripheral devices. It detects a dial tone and the hook status of the external tele-
phone from the current flowing through the line.
When a dial tone is input from the telephone line, current flows through the line. The line current detec-
tion IC sends the REVA and REVB to the ASIC as pulse signals. This allows a dial tone to be detected.
Signal Name Type Active Description Destination
REVA I - Line current detect signal ASIC
REVB I - Current reverse line current detect signal ASIC
CN3
Lb
R25
Line
REVA
REVB
19
4 20
1
2
8
7
19
20
36
37
NCU PBA Main PBA
IC38
ASIC
(I/O port)
CN4
CN16
IC2
Line current
detection IC