Sharp UX-177 Service Manual page 50

UX-177H
5. Pulse transmitting block
This block is composed of transistor (Q1), photo coupler (PC5)
and zener diode. Dial pulses supplied from CPU are amplified by
transistor (Q1) through a photo coupler (PC4) to the telephone
line.
6. ON-hook block
This block is composed of CML relay (CML), and CML is for
connection of the telephone line.
7. Hook detection block
This block is composed of hook switch (SW1), and is used to
detect on/off of the hook switch and to inform CPU of connec-
tion/open of the telephone line.
8. Communication circuit block
This block is composed of the speech IC (IC1), and is equipped
with 2-line/4-line select circuit, auto pad circuit, and all other cir-
cuit.
9. Speaker amplifier block
This block is composed of the speech amplifier IC (IC101), and is
used to amplify voice signal in monitoring or in speaker reception
with the amplifier IC and to supply to the speaker.
Signal flow when TEL speaking
CML
SURGE LINE
TEL LINE PROTECTION FILTER
BLOCK BLOCK
POLARITY
ON-HOOK
GUARD
BLOCK
BLOCK
CI DETECTION
CIRCUIT
10. Power supply
+24V and +5V are supplied from the control unit through the
connector CNLIUA-1~3.
11. Sensor block
This block is composed of PSNS (PE1), and is used to sense the
presence of recording paper and the cover open/close of the
cover.
12. Signal selection
The following signals are used to control the transmission line of
TEL/FAX signal.
•
TEL MUTE : Controls the mute of handset voice transmission
signal.
•
REC MUTE: Controls the mute of handset voice reception sig-
nal.
•
SP-MUTE: Controls the mute of speaker amplifier.
•
MPX A: Mutes the transmission drive amplifier.
H: Selected when the FAX signal is being re-
L: Selected when the telephone is being used or
DIAL PULSE SPEECH
GENERATION CIRCUIT
BLOCK BLOCK
DIAL
CONTROL
BLOCK
~
~
5 – 9
ceived
when the FAX signal is being transmitted
RX
HANDSET
TX
SPEAKER
AMP
SPEAKER
DOOR/PAPER
SENSOR
LED
HOOK
SW
REC MUTE
TEL MUTE
SIG TX
MODEM
MPX-A
SIGRX
MODEM
CML
CI
SP
PAPS
LED
RHS