UX-B20U/UX-B20C/B25C
5 – 15
[3] Circuit description of LIU PWB
1. LIU block operational description
1.1. Block diagram
1.2. Circuit description
The LIU PWB is composed of the following 7 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
7. Power supply and bias circuit
1.3. 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: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. CI detection circuit
• CI is detected by the photo coupler which is integrated in series in
the primary side TEL circuit well proven in the existing unit.
LINE
RX
TX
HANDSET
LIU PWB
CONTROL PWB
IC5 SCE209L
FAX ENGINE
IC4 UPD65945
ASIC
CML
CI DETECTOR
IC101A
OP AMP
OP AMP
OP AMP
OP AMP
IC101B
OP AMP
IC101C
OP AMP
IC101D
OP AMP
IC6
T1
TXOUT
SIGTX
SPKRP
0,20dB
Mute,0,-6,-12dB
Line In Enable
Line Out Enable
LninSel
1,1
0,0
0,0
1,1
RTLoop
DAC
SIN
LPF
ADC
SOUT
(20438 I/A)
SPKRN
SPOUT
SPMUTE
(H:MUTE)
SPEAKER
PH
SP Out Enable
Mic Enable
Mic/
Line
Sel
ect
LINEOUT
SIGRX
MICP
RXIN
C
C
E
B
4
5
3
TELMUTE
(H:MUTE)
DG
C
E
B
TELMUTE
(H:MUTE)
DG
C
E
B
DG
DG
C
E
B
DG
DG
DTMFMUTE
RCVOL
SPMUTE
TELMUTE
MICMUTE
CI
CML
RHS
+24V
+5V
DG
Fig. 6
Summary of Contents for UX-B20
Page 2: ... i UX B20U UX B20C B25C ...