Service manual

2. On-hook status detection circuit
The on-hook status detection circuit detects the Status of the hook
switch (RHS) of Built-in telephone, and the status of the hook of a
telephone externally connected.
• The status of on-hook switch (RHS) is determined from the
logical level of RHS signal.
RHS LOW: ON-HOOK
RHS HIGH: OFF-HOOK
• External telephone hook status detection circuit (HS1)
This circuit comprises the photo-coupler PC1, resistors R3 and
R4, Zener diodes ZD1 and ZD2.
When an external telephone is connected and enters the on-hook
mode, the LED of photo-coupler PC1 emits light and the light
receiving element turns on. The status signal HS1 is input to the
pin 84 of (XFCR-MVP) (IC4: control PWB).
HS1 LOW: EXT. TEL OFF-HOOK
HS1 HIGH: EXT. TEL ON-HOOK
3. Dial pulse generation circuit
The pulse dial generation circuit comprises the CML relay.
4. CML relay
The CML relay switches over connection to the matching trans-
former T1 while the FAX or built-in telephone is being used.
5. Matching transformer
The matching transformer performs electrical insulation from the
telephone 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
IC2 of operational amplifier, transmits the voice transmission sig-
nal to the line, and feeds back the voice signal to the voice recep-
tion circuit as the side tone.
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]
Signal Name Description
CML
Line connecting relay and DP generating
relay
H: Line make
L: Line break
SP MUTE
Speaker tone mute control signal
H: Muting (Power down mode)
L: Muting cancel (Normal operation)
TEL MUTE
Handset reception mute control signal
H: Muting
L: Muting cancel
RCVOL
Handset receiver volume control signal
(The circuit is located
in the control PWB.)
SIDE KICK is two-stage switching.
Note: The DTMF sending listed above is DTMF signal
sending in the handset OFF-HOOK mode.
VOL A
VOL B
VOL C
(The circuit is located
in the control PWB.)
Speaker volume control signal,
TXCONT
(The circuit is located
in the control PWB.)
TXOUT mute signal
H: Signal sending, when transmitting
L: During reception, transmission mute,
(during standby)
GAIN-C
(The circuit is located
in the control PWB.)
Reception gain switching signal
L: When connected to line, 1: 1 gain
H: When not connected to line, HIGH gain
MPX A
(The circuit is located
in the control PWB.)
Transmission/transfer switching signal
H: When transmitting modem signal
(during standby)
L: When transferring
BZCONT
(The circuit is located
in the control PWB.)
Speaker output signal switching
H: Buzzer signal output
L: When monitoring line signal
Volume High Middle DTMF sending
RCVOL H L L
VRSEL1 VRSEL2 matrix
VOL A VOL B VOL C
RING./
Receiving
Buzzer DTMF
L L L High — High
H L L Middle Fixed Middle
L L H Low — Low
UX-510U/UX-510C/UX-500U
UX-500C/FO-1460U
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