Service manual

UX-510UA
FO-1470U
[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 7 blocks.
1. Speech circuit section
2. Dial transmission section
3. Speaker amplifier section
4. Ringer circuit section
5. Externally connected TEL OFF HOOK detection circuit
6. CI detection circuit
7. Signal/DTMF transmission level & receiving level
Fig. 6
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.)
• DTM 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 – 8
DTMFMUTE
CONTROL PWBTEL/LIU PWB
RX
TX
HANDSET
SP
DRIVER
HS
CI
CSWI
PESNS
FRSNS
ORGSNS
PSNS
LEDON
BZOUT
CML
SPMUTE
RCVOL
VTHON
FAX
ENGINE
SCE114
ADC
DAC
SIN
DAC GAIN
0,6dB
SOUT
ADC GAIN
0,–4dB
MIC IN
LPF
LINE IN
LPF
SP OUT
ENABLE
0,20,25,30dB
LINE
DRIVER
LINEOUT
ENABLE
MUTE,0,
–6,–12dB
RHS
DRSNS
TXMUTE
TELMUTE
IA-RESET
SPMUTE
SPEAKER
RCV VOL
TELMUTE
TELIN
CI
M
B
C
CML
L1
L2
INTEGRATED ANALOG
20415
TELOUT
RXIN
TXOUT
SPKRP-P
MICP
LINEIN
LINEOUT
RTLOOP
(0:1)
(1:0)
(0:0)
(1:1)
MIC ENABLE
MIC
ENABLE
1
0
LINE IN
ENABLE
1
0
(0:0)
(1:1)
(1:0)
LNINSEL
IACR1
IACR2
IACR3
BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0
DAC
GAIN
MIC GAIN L/O E
SPKR E
ADC
GAIN
L/I E MIC E
TXRX
LOOP
LINEOUT
ATTENUATION
RXTXLOOP
MICBIAS
SEL
LINE SEL
MIC
GAIN
DTMFMUTE