Circuit Description Of Tel/Liu Pwb - Sharp UX-1100 Service Manual

[3] Circuit description of TEL/LIU PWB

(1) TEL/LIU block operational description
1) Block diagram
E-RLY
L
EARTH
H
CML
HOOK
TEL LINE
DETC.
EXT. TEL
2) Circuit description
The TEL/LIU PWB is composed of the following 9 blocks.
1. Surge protection circuit
2. External telephone hook status detection circuit
3. Dial pulse generation circuit
4. CML relay
5. Matching transformer
6. Buzzer circuit
7. Sensor circuit
8. Cl detection circuit
9. Power supply and bias circuit
H
H
L
L
H
DP
L
Q-RLY
CI
DETECTOR
TEL/LIU PWB CONTROL PWB
TXOUT
H
L
RX IN
TEL IN
TEL OUT
SPOUT
BUZZER
Fig. 6
3) Block description
1. Surge Protection circuit
This circuit protects the circuit from the surge voltage occurring on
the telephone line.
•
The AR2,3 protects the circuit from the 500V or higher line
surge voltages.
5 – 9
UX-1100DE
FO-1450DE
HS
PC-RLY
CML
SEL A
SEL B
MPX B
MPX A
SIG TX
SIG RX
SEL C SEL C
VOL C
VOL B
VOL A
VOL C
VOL B
VOL A
BZ
MPX C MPX C
SP MUTE
TEL MUTE
CI