Toshiba GD-1221 Manual Do Utilizador
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GD-1220/1221
ELECTRICAL CIRCUITS
4 - 9
4
EU/AU/AS/C models
Fig. 4-9
The line current detection circuit consists of the line current detection IC (IC2), ASIC (IC23) on the
MAIN board, and the other peripheral devices. It detects a dial tone and the hook status of the external
telephone from the current flowing through the line.
MAIN board, and the other peripheral devices. It detects a dial tone and the hook status of the external
telephone 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 REVA1 and REVB1 to the ASIC as pulse signals. This allows a dial tone to be detected.
tion IC sends REVA1 and REVB1 to the ASIC as pulse signals. This allows a dial tone to be detected.
Signal Name
Type
Active
Description
Destination
REVA1
I
-
Line 1 Current Detection Signal
IC23
REVB1
I
-
Current Reverse Line 1 Current Detection
Signal
IC23
CN3
Lb
R26
Line
REVA1
REVB1
19
4
20
1
2
8
7
19
20
160
161
NCU board
FAX board
IC23
ASIC
CN4
CN262
IC2
Line current
detection
IC
CN5
66
33
CN5
MAIN board
66
33