Sharp UX-108, Service Manual

Page: 52 / 96

UX-108DE
5 – 9
2. Noise filter
The noise filter comprises the RF choke coil, L4A, L4B.
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 IC101
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.
Signal Name Description
CML Line connecting relay and DP generating relay
(The circuit is located
H: Line make
in the TEL/LIU PWB.)
L: Line break
SP MUTE Speaker tone mute control signal
(The circuit is located
H: Muting (Power down mode)
in the TEL/LIU PWB.)
L: Muting cancel (Normal operation)
Handset reception mute control signal
RX MUTE H: Muting
L: Muting cancel
DP generating relay
DP ON H: DP make
L: DP break
Speaker volume control signal
VOL A VRSEL1 VRSEL2 matrix
VOL B
VOL C
(The circuit is located
in the control PWB.)
TXCONT
TXOUT mute signal
(The circuit is located
H: Signal sending, when transmitting
in the control PWB.)
L: During reception, transmission mute,
(during standby)
GAIN-C Reception gain switching signal
(The circuit is located
L: When connected to line, 1: 1 gain
in the control PWB.)
H: When not connected to line, HIGH gain
BZCONT Speaker output signal switching
(The circuit is located
H: Buzzer signal output
in the control PWB.)
L: When monitoring line signal
7. Signal selection
The following signals are used to control the transmission line of TEL/
FAX signal. For details, refer to the signal selector matrix table.
[Control signals from output port]
VOL A VOL B VOL C RING SP.REC.
BUZZER
/DTMF
H L L High High —
L H L — Middle —
L L H
Middle — —
L L L Low Low Fixed