Circuit Description Of Tel/Liu Pwb - Sharp UX-370SE Service Manual

UX-370ES/SE/F
FO-780AT/ES
[3] Circuit description of TEL/LIU PWB (UX-370ES/SE/FO-780AT/ES)
(1) TEL/LIU block operational description
1) Block diagram
CML
TEL
H
LINE
L
EXT.
CI DETECT
H
L E-RLY
TEL
(RCVOL)
H
EARTH
L
TELMUTE
HANDSET
L
RX
H
DG
TX
2) Circuit description
The TEL/LIU PWB is composed of the following 10 blocks.
1. Surge protection circuit
2. Noise filter
3. Dial pulse generation circuit
4. CML relay
5. Matching transformer
6. Hybrid circuit
7. Signal selection
8. Sensor circuit
9. Cl detection circuit
10. Power supply and bias circuit
DPON
(MPXB)
H
~ +
L
~ –
H
HS AGC
L
DPMUTE
(MPXC)
L
H
L
ON
H
HOOK
OFF
DG HOOK
TEL/LIU PWB CONTROL PWB
E-RLY RCVOL
CML CML
RLYCONT RCVOL2
DPON DPON
DPMUTE DPMUTE
CI CI
HS HS
TXMUTE
L
SIGMUTE
H
TXOUT
TXOUT
SIDETONE
CANCELER
RXIN RXIN
EXTING
TEL IN TEL IN
TEL OUT TEL OUT
HOOK SW
H
RHS RHS
L
TEL MUTE TEL MUTE
SPEAKER
Fig. 5
3) Block description
1. Surge Protection circuit
This circuit protects the circuit from the surge voltage occurring on the
telephone line.
•
The AR1, AR2 protects the circuit from the 425V or higher line
surge voltages.
5 – 8
GAINC
L
H
HI GAIN
H TXCONT
L
L
H
VREF
SPMUTE
L
L
BZOUT
H
H
VOL B
VOL A
DG
RCVOL
RCVOL2
DPMUTE
MODEM
(R96DFXL-CID)
TXMUTE
VOL B
VOL A
TXOUT
RXIN
GAINC
CI
HS
TXCONT
RHS FC100M
SPMUTE
DPON
BZCONT
CML
TEL MUTE
PE9