Circuit Description Of Tel/Liu Pwb - Sharp UX-340L Service Manual

UX-340L/UX-345L
UX-330L

[3] Circuit description of TEL/LIU PWB

(1) TEL/LIU block operational description
1) Block diagram
CML
TEL
HS DETECTOR
LINE
EXT.
HANDSET
SPEAKER
L H
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
TX OUT
H
L
RX IN
CI DETECTOR
TEL IN
TEL OUT
SP AMP
SP OUT
VOL A
CONTROL PWB
CML
TX CONT
1
0
0
1
0
1
VOL B
Fig. 5
3) Block description
1. Speech circuit section
•
The receiver volume is an electronic volume type, this model is
switched in 2 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
•
The volume of the ringer sound/speaker sound is controlled with
2-bit signal of VOLA and VOLB, and the sound switch is controlled
with BZ CONT.
4. Ringer circuit section
•
The ringer sound is formed in the tone of 1-chip modem when CI
signal is detected. The amplifier circuit drives the speaker of the
main body.
5 – 8
GAIN-C
SIGTX
(R96DFXL-CID)
SIGRX
BZOUT
FC100M
BZ CONT
SP MUTE
TEL MUTE
CI
HS
MODEM
GAIN-C
TXCONT
CML