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January 2001 © TOSHIBA TEC
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GD-1060 CIRCUIT DESCRIPTION
The line monitor circuit consists of the CML relay (NAD/SAD/TWD models: RLY2, ASD/AUD/CND/MJD
models: RLY3), analog switch (NAD/SAD/TWD models: IC51, ASD/AUD/CND/MJD models: IC3), the I/O
port GA-2 (IC6) and analog switches (IC4, IC5) on the Main PWA, and other peripheral devices. It switches
the telephone line path with the analog switch and monitors the line status, pseudo-ring signal, and tone
signal in facsimile transmission and reception with the speaker connected to CN47 on the Relay PWA. It
also switches the analog switch to output a buzzer tone from the speaker.
The signal to be monitored is selected by switching the analog switch (IC4) according to the TONESEL
signal and RING/TONE signal, which are output from the I/O port GA-2.
To monitor the line during transmission and reception, the I/O port GA-2 causes the CML1 signal to be
HIGH to switch the analog switch and connect the line to the MODEM side.
For line path switching control, refer to “4. 1 Line Path Switching Control Circuit” in this chapter.
The correspondence between the respective signal levels and monitoring signals is shown in the table
below.
The monitoring signal selected by IC4 is input to the analog switch (IC5) to select an output sound volume.
The sound volume is controlled according to the SPVOL0-2 signals output from the I/O port GA-2.
The correspondence between the respective signals and sound volumes is shown in the table below.
The monitoring signal volume-controlled by IC5 is amplified by the OP amplifier (IC7) on the Relay PWA
and output to the speaker.
Monitoring signal
TONESEL
RING/TONE
Line monitor
HIGH
-
Pseudo-ring
LOW
HIGH
Alarm/Key touch Tone
LOW
LOW
Sound volume
SPVOL2
SPVOL1
SPVOL0
Silent (0)
LOW
LOW
LOW
Min. (1)
LOW
LOW
HIGH
(2)
LOW
HIGH
LOW
(3)
LOW
HIGH
HIGH
(4)
HIGH
LOW
LOW
(5)
HIGH
LOW
HIGH
(6)
HIGH
HIGH
LOW
Max. (7)
HIGH
HIGH
HIGH
Signal Name
I/O
Active
Description
Destination
TONESEL
O
H
Tone Select Signal
IC4
RING/TONE
O
H
Ring/Tone Select Signal
IC4
SPVOL0-2
O
H
Speaker Volume Control Signals 0-2
IC5