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
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-
ceived
L: Selected when the telephone is being used or
when the FAX signal is being transmitted
DIAL
CONTROL
BLOCK
POW1
POW4
~
COW1
COW4
~
CML
ON-HOOK
BLOCK
MODEM
REC MUTE
TEL MUTE
TEL LINE
SURGE
PROTECTION
BLOCK
DIAL PULSE
GENERATION
BLOCK
HANDSET
RX
LINE
FILTER
BLOCK
POLARITY
GUARD
BLOCK
SPEECH
CIRCUIT
BLOCK
TX
SIG TX
MPX-A
SIGRX
CML
CI
CI DETECTION
CIRCUIT
MODEM
SP
SPEAKER
AMP
SPEAKER
PAPS
DOOR/PAPER
SENSOR
LED
LED
RHS
HOOK
SW
UX-177H
5 – 9
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