Circuit Description Of Tel/Liu Pwb; Tel/Liu Block Operational Description - Sharp FO-71 Service Manual

FO-71RA
FO-51RA

[3] Circuit description of TEL/LIU PWB

(1) TEL/LIU block operational description

1) Block diagram
LINE H
L
CML
CI DETECTOR
PC2
Q103
RX
TEL MUTE
(H:MUTE)
TX
HANDASET
MIC MUTE
(H:MUTE)
Q105
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
TEL/LIU PWB CONTROL PWB
IC102
TXOUT
RXIN
IC102
IC101
TEL IN
IC101
SPEAKER
SP MUTE
(H:MUTE)
+24VL
DG
SIGTX SPKRP
SP OUT
SIGRX
MICP
MIC
/LINE
SELECT
LINEIN
LINE IN ENABLE
MODEM BLOCK
(CX20438 I/A)
SPOUT
LINE
OUT
IC5
DTMFMUTE
RCVOL
SP MUTE
TEL MUTE
CI
CML
MIC MUTE
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
•
Speaker volume :It is controlled by the attenuator value of the
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
RTLOOP
0,1
0,0
1,0
1,1
ENABLE
MIC ENABLE
LPF
0,20,25,30dB
LINE OUT ENABLE
LINE
SELECT
1,1
0,0
1,0
MUTE,0,-6,-12dB
IC2 SCE209
FAX CONTROLLER
: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.
LINE DRIVER in the modem.
0,6dB
SIN
DAC DAC
ADC
0,+4dB
SOUT