Circuit Description Of Tel/Liu Pwb - Sharp FO-1470 Service Manual

[3] Circuit description of TEL/LIU PWB

(1) TEL/LIU block operational description
1) Block diagram
L1
CML
M
C
L2
B
CI
HANDSET
RX
TX
BIT7 BIT6 BIT5 BIT4 BIT3
DAC
SPKR E
IACR1 MIC GAIN L/O E
GAIN
TXRX LINEOUT
IACR2
LOOP ATTENUATION
IACR3
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
TEL/LIU PWB CONTROL PWB
TXOUT
RXIN
TELIN
TELMUTE
DTMFMUTE
TELOUT
SPEAKER
BIT2 BIT1 BIT0
ADC
L/I E MIC E
GAIN
MICBIAS
RXTXLOOP
SEL
LINE SEL
SP OUT
ENABLE
SPKRP-P
SP
DRIVER
MIC
GAIN
MICP
0,20,25,30dB
LINEIN
RCV VOL
LINE
DRIVER
LINEOUT
MUTE,0,
LINEOUT
–6,–12dB
ENABLE
SPMUTE
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
•
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 – 8
INTEGRATED ANALOG
20415
RTLOOP
(0:1)
MIC ENABLE
(1:0)
(0:0)
DAC
(1:1)
DAC GAIN
0,6dB
MIC
ENABLE
1
MIC IN
LPF 0
ADC
LINE IN
ENABLE
ADC GAIN
1
LINE IN
0,–4dB
LPF 0
LNINSEL
(0:0)
(1:1)
(1:0)
BZOUT
CML
SPMUTE
FAX
ENGINE
DTMFMUTE
SCE114
RCVOL
VTHON
: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.
UX-510UA
FO-1470U
SIN
SOUT
HS
CI
CSWI
PESNS
FRSNS
ORGSNS
PSNS
LEDON
RHS
DRSNS
TXMUTE
TELMUTE
IA-RESET