Panasonic KX-AT7730RU (serv.man2) Service Manual ▷ View online
10
KX-AT7730 Series
4.2.4.
TONE GENERATION CIRCUIT
Function:
This circuit generates all system tones including COL, extension, busy, DTMF signals and key in confirmation tones during the
power failure mode and is comprised of IC1(DTMF Generator) and IC5 (Analog Switch).
Circuit Operation:
power failure mode and is comprised of IC1(DTMF Generator) and IC5 (Analog Switch).
Circuit Operation:
For an output of a single row tone, the row terminal and the each column terminals intersecting with it are required to be brought a
low state. For a dual tone output, one row terminal and one column terminal are brought to low state.
low state. For a dual tone output, one row terminal and one column terminal are brought to low state.
CONDITION
IC1 pin52
IC5 SWA
IC1 pin53
IC5 SWB
IC1 pin54
IC5 SWC
IC1 pin55
IC5 SWD
Ringing
L
OFF
L
OFF
L
OFF
H
ON
Call Waiting
L
OFF
L
OFF
H
ON
L
OFF
Tone Dial (Handset)
H
ON
H
ON
L
OFF
L
OFF
Tone Dial (Speakerphone) H
ON
L
OFF
H
ON
L
OFF
Circuit Diagram
C28
R31
R30
C29
C84
C31
Q8
R84
IC1
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
R124
R123
A5V
T_CONT1
T_CONT3
T_CONT4
R81
C81
T_CONT2
T_CONT1
T_CONT2
T_CONT3
T_CONT4
C63
C61
AG
C66
AG
R80
CN3
1
+
2
-
C67
R85
AG
Parity Circuit Board 1
P3_5
P3_4
P3_3/*INT3
P2_7
P2_6
P2_5
P2_4
P2_3
P2_2
P2_1
P2_0
P3_6
P3_1
P8_6
P8_5
P8_4
P8_3
P8_2
P8_1
P8_0
P6_7
P6_6/TXD2
P6_5/CLK2
P4_5
P1_7
P1_6
P1_5
P1_4
P1_3
P1_2
P1_1
P1_0
P0_
7/DA1
P0_
6/DA0
P0_5
T_CONT1
P0_3
P0_2
P0_1
P0_0
P6_4
P6_3
P6_2
P6_1
P6_0
P5_7
P5_6
P3_2
P3_0
P4_2/VREF
MODE
HS_MUTE
P4_4/XCOUT
*RESET
P4_7/XOUT
VSS/AVSS
P4_6/XIN
VCC/AVCC
P5_4
P5_3
P5_2
P5_1
P5_0
P3_7
IC5
1
I/O1
2
O/I1
12
CONT4
13
CONT1
3
O/I2
14
VDD
4
I/O2
11
I/O4
5
CONT2
10
O/I4
6
CONT3
9
O/I3
7
VSS
8
I/O3
R82
R86
R87
C82
NC
AG
D3.3V
R88
AG
D3.3V
AG
R296
NC
AG
AG
C85
C86
IC8
1
IN/OUT
2
OUT/IN
3
GND
5
VCC
4
CONT
AG
R89
68k
D3.3V
R144
470
R90
470
AG
AG1
K1
K2
N1
N2
N3
N4
CN7-6
CN8-1
CN8-5
CN7-7
CN7-3
CN8-2
Q18
SW1
4
C
1
2
3
5
6
RING_OFF
CN8
CN7
C6
C7
R9
R10
R7
C5
NC
AG
R8
AG
T1
1
6
3
4
2
Q3
C4
C14
IC3
1
RR
2
RTX
3
TXI
4
TXO
5
TLI
23
XDC
24
VLC
25
ACF
26
RXO
27
RXI
6
TLO
7
RLI
8
RLO
9
MCI
10
MCO
12
CP2
13
XDI
14
SKG
18
*CS
19
SKI
20
VCC
21
VB
22
GND
15
SKO
16
V+
17
AGC
11
CP1
28
RRX
L4
R79
R78
+6V
AG
0
R61
11
KX-AT7730 Series
4.2.5.
HANDSET CIRCUIT
1) Transmission Signal Path
The input signal for the handset microphone is sent through the telephone line via the following path:
Handset MIC(JK2)
Handset MIC(JK2)
→ JK3 → C24 → R26 → C34 → Q5 → C21 → R21 → Q3 → C4 → T1 → C3 → Q1 → D1 → Telephone Line
2) Reception Signal Path
The input signal from the telephone line is sent to the receiver through the following path:
Telephone Line
Telephone Line
→ D1 → Q1 → C3 → T1 → C4 → Q3 → R10 → C8 → R12 → Q4 → C26 → R32 → IC10 → C32 → R34 → C27 →
R208
→ Q8 → C31 → JK3 → JK2 → Handset Speaker
C21
T1
1
3
4
6
C3
C2
R4
R1
R2
JK1
1
H
2
T
3
R
4
L
D1
4
3
1
2
R21
R41
R8
R9
R15
R16
R14
+6V
R13
C8
R12
R10
C9
PC1
1
2
3
4
R3
R5
NC
C1
R7
R6
C4
C41
AG
AG
AG
AG
H
T
R
L
NC
C11
NC
C10
C6
NC
C5
Q3
Q4
Q2
Q1
DG
R17
NC
C13
C12
C7
C14
D9
Q11
1
B1
2
E
3
B2
4
C2
5
C1
Q12
1
B1
2
E
3
B2
4
C2
5
C1
IC5
1
I/O1
2
O/I1
12
CONT4
13
CONT1
3
O/I2
14
VDD
4
I/O2
11
I/O4
5
CONT2
10
O/I4
6
CONT3
9
O/I3
7
VSS
8
I/O3
C24
C27
C34
C208
C213
C22
C29
C84
C23
C209
C28
C30
R31
R30
R73
R23
R36
R37
R208
R24
R22
R84
R26
R25
R29
R27
R74
C207
NC
AG
R19 NC
R20 NC
AG
AG1
AG
AG
C214 NC
D3.3V
AG
G
A
G
A
AG
R38
AG
JK2
1
2
3
4
2
3
4
5
JK3
1
2
5
3
4
4
C211
N5
N6
N7
N8
SP1
SP2
M2
M1
AG1
R28
CN8-3
CN8-6
CN8-4
CN8-7
CN7-5
CN7-4
CN7-1
CN7-2
Q6
Q10
Q21
Q22
AG
A5V
J2
NC
J3 NC
Q5
Q8
R39
R40
C250
L1
L7
NC
L6 NC
C25
C31
L5
D41
NC
CN8
CN7
Split PCB 1
D30
C131
C32
C33
C130
R240
R231
C26
R32
R289
R76
R238
R234
R230
R233
R237
R236
R77
AG
AG
AG
R235
N
C
C133
NC
AG
AG
AG
AG
AG
AG
R34
IC10
1
AOUT
2
A-IN
3
A+IN
4
GND
5
B+IN
6
B-IN
7
BOUT
8
V+
Q9
C132
C35
C36
R232
L2
Circuit Diagram
HEAD SET
HS_VOL2
HS_VOL1
HS_MUTE
T_CONT2
12
KX-AT7730 Series
4.2.6.
SPEAKERPHONE CIRCUIT
Function:
This circuit controls the automatic switching of the transmitted and received signals to and from the telephone line, when the unit is
used in the hands-free mode.
used in the hands-free mode.
Circuit Operation:
The speakerphone can only provide a one-way communication path at a given time, but cannot do both simultaneously.
Therefore, a switching circuit is necessary to control the flow of the outgoing and incoming signals.
In other words, it can either transmit an outgoing signal or receive an incoming signal at a given time, but cannot do both
simultaneous. Therefore, a switching circuit is necessary to control the flow of the outgoing and incoming signals.
This switching circuit is contained in IC3 and consists of a Voice Detector, Tx Attenuator, Rx Attenuator, Comparator and Attenuator
Control. The circuit analyzes whether the Tx (transmit) or Rx (receive) signal is louder, and then it processes the signals so that the
louder signal is given precedence.
The Voice Detector provides a DC input to the Attenuator Control corresponding to the Tx signal. The Comparator receives a Tx
and Rx signal, and supplies DC input to the Attenuator Control corresponding to the Rx signal.
The Attenuator Control provides a control signal to the Tx and Rx Attenuator to switch the appropriate signals ON and OFF.
The Attenuator Control also detects the level of the volume control to automatically adjust the volume for changing ambient
conditions.
Therefore, a switching circuit is necessary to control the flow of the outgoing and incoming signals.
In other words, it can either transmit an outgoing signal or receive an incoming signal at a given time, but cannot do both
simultaneous. Therefore, a switching circuit is necessary to control the flow of the outgoing and incoming signals.
This switching circuit is contained in IC3 and consists of a Voice Detector, Tx Attenuator, Rx Attenuator, Comparator and Attenuator
Control. The circuit analyzes whether the Tx (transmit) or Rx (receive) signal is louder, and then it processes the signals so that the
louder signal is given precedence.
The Voice Detector provides a DC input to the Attenuator Control corresponding to the Tx signal. The Comparator receives a Tx
and Rx signal, and supplies DC input to the Attenuator Control corresponding to the Rx signal.
The Attenuator Control provides a control signal to the Tx and Rx Attenuator to switch the appropriate signals ON and OFF.
The Attenuator Control also detects the level of the volume control to automatically adjust the volume for changing ambient
conditions.
1) Control Signal Path
Control signal for transmission and reception are input to IC3 via the following path:
(Transmission Control Signal Path)
MIC(CN2)
(Transmission Control Signal Path)
MIC(CN2)
→ IC3 Pin 9 → IC3 Pin 10 → IC3 Pin 3 → IC3 Pin 4 → IC3 Pin 5
(Reception Control Signal Path)
Telephone Line
Telephone Line
→ Q3 → Q4 → IC3 Pin 7
2) Transmission/Reception Switching
The comparison result between Tx and Rx output is a DC level at IC3 Pin 25.
Tx level is high .................... Pin 20-Pin 25=6mV
Rx level is high .................... Pin 20-Pin 25=150mV
The comparator output is connected to the attenuator control inside IC3.
Tx level is high .................... Pin 20-Pin 25=6mV
Rx level is high .................... Pin 20-Pin 25=150mV
The comparator output is connected to the attenuator control inside IC3.
3) Voice Detector
The output of the mic amp (Pin 10 of IC3) is supplied to Pin 13 of IC3 as a control signal for the voice detector.
4) Attenuator Control
The attenuator control detects the setting of the volume control through Pin 24 of IC3 and automatically adjusts the volume for
changing ambient conditions.
changing ambient conditions.
5) Transmission Signal Path
The input signal from the microphone is sent through the circuit via the following path:
MIC(CN2)
MIC(CN2)
→ C64 → R206 → C59 → IC3 Pin 9 → IC3 Pin 10 → R45 → C48 → IC3 Pin 3 → IC3 Pin 4 → C41 → R41 → Q3 → C4
→ T1 → C3 → Q1 → D1 → JK1 → Telephone Line
6) Reception Signal Path
Signals received from the telephone line are output to the speaker via the following path:
Telephone Line
Telephone Line
→ D1 → Q1 → C3 → T1 → C4 → Q3 → R10 → C8 → R12 → Q4 → C42 → R42 → C46 → IC3 Pin 27 →
IC3 Pin 26
→ R57 → C62 → C61 → IC3 Pin 19 → IC3 Pin 15 → L4 → C63 → CN3 Speaker
7) Busy Tone Detector Circuit
The busy tone detection for automatic redialing is executed as follows.
Telephone Line
Telephone Line
→ D1 → Q1 → C3 → T1 → C91 → R91 → IC6 → D3 → R99 → Q20 → IC1 Pin 64
13
KX-AT7730 Series
Q15
SP_VOL1
SP_VOL2
SP_VOL3
SP_VOL4
1
B1
2
E
3
B2
4
C2
5
C1
Q16
1
B1
2
E
3
B2
4
C2
5
C1
C50
C51
C48
C59
C61
C64
C60
C47
C49
C44
C45
C46
C62
0.047u
C66
C67
R206
R52
R59
R68
R60
R55
R54
R57
R67
R48
R70
R51
R49
R45
R80
R79
R44
R78
R46
R47
R69
R50
R56
AG
AG
AG
NC
AG
AG
AG
+6V
AG
AG
+6V
AG
AG
C57
AG
G1
G2
AG
Q13
Q14
C53
C54
R72
R58
IC3
1
RR
2
RTX
3
TXI
4
TXO
5
TLI
23
XDC
24
VLC
25
ACF
26
RXO
27
RXI
6
TLO
7
RLI
8
RLO
9
MCI
10
MCO
12
CP2
13
XDI
14
SKG
18
*CS
19
SKI
20
VCC
21
VB
22
GND
15
SKO
16
V+
17
AGC
11
CP1
28
RRX
L3
C251
AG
C252
C253
AG
C254
220p
AG
C255
L4
C52
C55
C58
C56
D3
C8
C42
C41
C91
C14
C93
C212
C6
C12
C7
R91
R93
R97
R99
R1
R96
R98
R14
R15
R92
R9
R12
R2
R10
R7
R5
R41
R13
R95
R16
R6
R4
AG
AG
AG
AG
AG
D3.3V
A5V
C5
NC
C13
NC
AG
AG
AG
C10
NC
AG
+6V
A5V
AG
R8
H
T
R
L
T
R
L
AG
JK1
1
2
3
4
5
T1
1
6
3
4
2
IC6
1
AOUT
2
A-IN
3
A+IN
4
GND
5
B+IN
6
B-IN
7
BOUT
8
V+
R17
Q3
Q4
Q20
IC1(64)
C94
R94
R100
C3
C92
C95
C96
D1
4
1
3
2
PC1
1
2
3
4
Q1
Q2
R3
C4
C2
C9
R43
NC
C43
C65
CN2
MIC
1
+
2
-
AG
M3
AG2
C63
R61
0
SP
CN3
1
+
2
-
AG
SP- SP+
R71
R42
Circuit Diagram
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