Sharp FO-2970M Service Manual page 58

FO-2970MU
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 IC1
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.
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
Line connecting relay and DP generating relay
CML H: Line make
L: Line break
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
Handset receiver volume control signal
RCVOL
Volume
RCVOL
(The circuit is located
in the control PWB.)
Set the line driver of MODEM (FM336)
to – 6 dBm
Speaker volume control signal
VOL A
VOL B
VOL A VOL B VOL C
VOL C
H
(The circuit is located
L
in the control PWB.)
L
L
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
(The circuit is located
L: When monitoring line signal
in the control PWB.)
MIC MUTE Handset mic mute control signal
H: Muting
L: Muting cancel
Description
High Middle Low
H L L
VRSEL1 VRSEL2 matrix
RING./
Buzzer DTMF
Receiving
L L High — High
H L Middle —
Middle
L H Low — Low
L L — Fixed —
[Signals for status recognition according to input signals]
Signal Name
RHS H: The handset is in the on-hook state.
(On the HOOK-SW PWB) L: The handset is in the off-hook state.
CI Incoming call (CI) detection signal.
H: The handset or external telephone is in the
on-hook state.
HS
L: The handset or external telephone is in the
off-hook state.
[Other signals]
Signal Name
TEL IN Receiving signal from line or modem
TEL OUT Transfer signal to line
Transmission (DTMF) analog signal output
TXOUT
from modem
Reception (DTMF, others) analog signal input
RXIN
into modem
No. Signal Name (CNLIU)
1 +24V
2 DG
3 +5VA
4 CML
5
CI
6 HS
No. Signal Name (CNHS 1 and 2)
1 RHS
8) CI detection circuit
The CI detection circuit detects the CI signals of 15.3 Hz to 68 Hz.
A CI signal, which is provided to the photo-coupler PC2 through the
C3 (0.82 uF), R3 (22 K), and ZD3 when the ring signal is inputted
from the telephone line.
9) Power supply and bias circuits
The voltages of +5VA and +24V are supplied from the control PWB
unit.
5 – 22
Function
Function
No. Signal Name (CNLIU)
7
RHS
8 TXOUT
9 RXIN
10 TELMUTE
11 TELOUT
12 TELIN
No. Signal Name (CNHS 1 and 2)
2
DG