FO-71RA
FO-51RA
[3] Circuit description of TEL/LIU PWB
(1) TEL/LIU block operational description
1) Block diagram
2) Circuit description
The TEL/LIU PWB is composed of the following 6 blocks.
1. Speech circuit section
2. Dial transmission section
3. Speaker amplifier section
4. Ringer circuit section
5. CI detection circuit
6. Signal/DTMF transmission level & receiving level
Fig. 5
3) Block description
1. Speech circuit section
• This circuit is composed by IC101,IC102 and that circumference
circuit.
2. Dial transmission section
• D.P. transmission: The CML relay is turned on and off for control in
the DP calling system. (Refer to the attached sheet.)
• DTMF transmission: It is formed in the modem, and is output.
3. Speaker amplifier section
• Ringer volume :It is controlled by the combination of the
attenuator value of the LINE DRIVER in the
modem and the ringer sending level sent from
the modem.
• Speaker volume :It is controlled by the attenuator value of the
LINE DRIVER in the modem.
4. Ringer circuit section
• The ringer sound is formed in the tone of modem when CI signal is
detected. The amplifier circuit drives the speaker of the main body.
5 – 9
DAC
LPF
DAC
H
L
CI DETECTOR
SPEAKER
LINE
+24VL
DG
CONTROL PWBTEL/LIU PWB
RX
TX
TEL MUTE
(H:MUTE)
PC2
Q103
IC102
Q105
IC101
IC101
IC102
IC5
0,1
0,0
1,0
1,1
RTLOOP
ADC
SIN
MIC
/LINE
SELECT
SP OUT
ENABLE
MIC ENABLE
LINE IN ENABLE
LINE OUT ENABLE
0,20,25,30dB
LINE
SELECT
1,1
0,0
1,0
0,+4dB
SOUT
MODEM BLOCK
(CX20438 I/A)
SPKRP
MICP
LINEIN
LINE
OUT
MUTE,0,-6,-12dB
IC2 SCE209
FAX CONTROLLER
DTMFMUTE
RCVOL
SP MUTE
TEL MUTE
CI
CML
MIC MUTE
SPOUT
SP MUTE
(H:MUTE)
TEL IN
RXIN
TXOUT
MIC MUTE
(H:MUTE)
CML
SIGTX
SIGRX
0,6dB
HANDASET
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