Circuit Description Of Tel/Liu Pwb - Sharp UX-A255U Service Manual

[3] Circuit description of TEL/LIU PWB

(1) TEL/LIU block operational description
1) Block diagram
LINE
H
L
CML
CI DETECTOR
PC1
Q101
RX
TEL MUTE
(H:MUTE)
TX
HANDSET
MIC MUTE
(H:MUTE)
Q102
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-B
TXOUT
RXIN
IC102-A
IC101-A
TEL IN
IC101-B
SPEAKER
IC5
IC7
SP MUTE
(H:MUTE)
+24VL
DG
MODEM BLOCK
(20438 I/A)
SIGTX
SPKRP
SIGRX MICP
/LINE
SELECT
LINEIN
LINE IN ENABLE
Q105
Q104
SPOUT
LINE
OUT
BZOUT1
DTMFMUTE
RCVOL
SP MUTE
TEL MUTE
CI
CML
MIC MUTE
VOL-A
VOL-B
VOL-C
Fig. 5
3) Block description
1. Speech circuit section
•
The receiver volume is an electronic volume type, this model is
switched in 3 steps.
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 – 10
RTLOOP
0,1
0,0
1,0
1,1
MIC ENABLE
SP OUT ENABLE
MIC
LPF
0,20,25,30dB
LINE OUT ENABLE
LINESEL
1,1
0,0
1,0
MUTE,0,-6,-12dB
IC3 SCE214V
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.
IC5 and IC3 (VOL-A,B,C)
UX-A255U
0,6dB
SIN
DAC DAC
ADC
0,+4dB
SOUT