Sharp UX-470 Service Manual page 37

2. Noise filter
The noise filter comprises the RF choke coil, L6, L7 and L8.
3. Dial pulse generation circuit
The pulse dial generation circuit comprises the photo-coupler PC2,
PC3, polarity guard REC1, and resistor R1.
The photo-coupler PC3 shunts the line current using the DP signal
before transmitting the dial signal, then turns off the CML relay.
After the pulse dial signal is transmitted by turning on/off the DP sig-
nal, the CML relay is turned on again.
4. CML relay
The CML relay switches over connection to the matching transformer
T1 while the FAX or built-in telephone is being used.
5. Matching transformer
The matching transformer performs electrical insulation from the tel-
ephone line and impedance matching for transmitting the TEL/FAX
signal.
6. Hybrid circuit
The hybrid circuit performs 2-wire-to-4-wire conversion using the IC102
of operational amplifier, transmits the voice transmission signal to the
line, and feeds back the voice signal to the voice reception circuit as
the side tone.
8. Sensor circuit
For the recording paper sensor (PE), when there is recording paper,
the photo transistor in the light receiving side is ON and the detection
level is LOW. When there is no recording paper, the photo transistor
in the light receiving side is OFF and the detection level is HIGH.
9. CI detection circuit
The CI detection circuit detects the CI signals. A CI signal, which is
provided to the photo-coupler PC6 through the ES: C3(0.47µF)/
R3(51K), SE: C3(0.56µF)/R3(22K), AT: C3(1.0µF)/R3(15K), and ZD2
when the ring signal is inputted from the telephone line.
10. Power supply and bias circuits
The voltages of +5V and +24VA are supplied from the control PWB
unit.
7. Signal selection
The following signals are used to control the transmission line of TEL/
LIU signal. For details, refer to the signal selector matrix table.
[Control signals from output port]
Signal Name
CML Line connecting relay and DP generating relay
H: Line make
(The circuit is located
L: Line break
in the TEL/LIU PWB.)
Speaker tone mute control signal
SP MUTE H: Muting (Power down mode)
L: Muting cancel (Normal operation)
Handset reception mute control signal
TEL MUTE H: Muting
L: Muting cancel
Speaker volume control signal,
OUTPUT VOL A VOL B VOL C
VOL A
VOL B
VOL C
(The circuit is located
in the control PWB.)
OUTPUT RINGER BUZZER
Handset transfer mute control signal
TXCONT
H: Signal sending, when transmitting
(The circuit is located
L: During reception, transmission mute,
in the control PWB.)
GAIN-C Reception gain switching signal
L: When connected to line, 1: 1 gain
(The circuit is located
H: When not connected to line, HIGH gain
in the control PWB.)
BZCONT Speaker output signal switching
H: Buzzer signal output (during stand by)
(The circuit is located
L: When monitoring line signal
in the control PWB.)
5 – 9
UX-470ES/SE/AT
FO-880ES/AT
Description
VOL A VOL B VOL C matrix
NEW OH-HOOK
R
X0 L L L 33K
X1 L L H 75K
X2 L H L 150K MIDDLE1
X3 L H H 300K MIDDLE2
X4 H L L 510K MIDDLE3
X5 H L H 470K
X6 H H L 750K
X7 H H H 100K
DTMF
X0 HIGH — —
X1 — —
X2 — — —
X3 — —
X4 LOW —
X5 — FIXED FIXED
X6 — —
X7 MIDDLE —
(during standby)
Receiving
—
HIGH
—
LOW
—
ICM/OGM
HIGH
MIDDLE1
MIDDLE2
MIDDLE3
—
LOW
—
—