Panasonic KX-TCD420RUT / KX-A142RUT Service Manual ▷ View online
20.2. Power Supply Circuit
The power is supplied to the DECT BBIC, RF Module, EEPROM, Relay Coil, LED and Charge Contact from AC Adaptor (+6V)
as shown in Fig.101. The power supply is as follows;
as shown in Fig.101. The power supply is as follows;
·
DECT BBIC (IC8): J1(+6V)
→
D4
→
IC2
→
IC3
→
IC8
→
IC6, IC7
·
RF Module (IC9): J1(+6V)
→
D4
→
IC2
→
IC9
·
EEPROM (IC4): J1(+6V)
→
D4
→
IC2
→
IC3
→
IC4
·
LED (LED1): J1(+6V)
→
D4
→
IC2
→
R57
→
LED1
·
Charge Contact (TP13): J1(+6V)
→
D4
→
R59, R60
→
TP13
<Fig.101>
57
KX-TCD420RUT / KX-A142RUT
20.3. Telephone Line Interface
<Function>
·
Bell signal detection
·
Clip signal detection
·
ON/OFF hook circuit
·
Audio circuits
Bell & Clip (: Calling Line Identification Presentation: Caller ID) signal detection:
In the standby mode, Q2 is open to cut the DC loop current and decrease the ring load.
When ring voltage appears at the TP3 (A) and TP40 (B) leads (when the telephone rings), the signal is transferred as follows;
·
A
→
C25
→
R40
→
R45
→
IC5
→
C28
→
R47
→
C29
→
R49
→
IC8 (136) [CLIP]
·
B
→
C24
→
R39
→
R44
→
IC5
→
C28
→
R47
→
C29
→
R49
→
IC8 (136) [CLIP]
·
A
→
C2
→
IC1
→
IC8 (81) [BELL]
·
B
→
D2
→
D3
→
R1
→
IC1
→
IC8 (81) [BELlL]
ON/OFF hook circuit:
In the standby mode, Q2 is open, and connected as to cut the DC loop current and to cut the voice signal. The unit is
consequently in an off-hook condition.
consequently in an off-hook condition.
When IC8 detects a ring signal or press the TALK Key onto the handset, Q4 turns on and then Q2 turns on, thus providing an
off-hook condition (active DC current flow through the circuit) and the following signal flow is for the loop current.
off-hook condition (active DC current flow through the circuit) and the following signal flow is for the loop current.
·
A
→
JMP9
→
D6
→
Q2
→
R13
→
Q4
→
D6
→
B [OFF HOOK]
20.4. Transmitter/Receiver
Base Unit and Handset mainly consist of RF Module and DECT BBIC.
Base Unit and Handset transmit/receive voice signal and data signal through the antenna on carrier frequency.
Signal Pass:
*Refer to SIGNAL ROUTE (P.61).
20.4.1. Transmitter Block
The voice signal input from the TEL LINE interface goes to RF Module (IC9) through DECT BBIC (IC8) as shown in BLOCK
DIAGRAM (BASE UNIT) (P.55)
DIAGRAM (BASE UNIT) (P.55)
The voice signal passes through the analog part of IC8 where it is amplified and converted to a digital audio stream signal. The
burst switch controller processes this stream performing encryption and scrambling, adding the various other fields to produce
the GAP (Generic Access Profile) standard DECT frame, assigning to a time slot and channel etc.
burst switch controller processes this stream performing encryption and scrambling, adding the various other fields to produce
the GAP (Generic Access Profile) standard DECT frame, assigning to a time slot and channel etc.
In IC3, the carrier frequency is changing, and frequency modulated RF signal is generated and amplified, and radiated from
antenna. Handset detects the voice signal or data signal in the circuit same as the following explanation of Receiver Block.
antenna. Handset detects the voice signal or data signal in the circuit same as the following explanation of Receiver Block.
20.4.2. Receiver Block
The signal of 1.152 MHz band (1.881792 MHz ~ 1.897344 MHz) which is input from antenna is input to IC9 as shown in BLOCK
DIAGRAM (BASE UNIT) (P.55).
DIAGRAM (BASE UNIT) (P.55).
In IC3, the signal of 1.152 MHz band is downconverted to 864 kHz signal and demoduleted, and goes to IC2 as GAP (Generic
Access Profile) standard DECT frames. It passes through the decoding section burst switch controller where it separates out
the frame information and performs de-encryption and de-scrambling as required. It then goes to the DSP section where it is
turned back into analog audio. This is amplified by the analog front end, and goes to the TEL LINE Interface.
Access Profile) standard DECT frames. It passes through the decoding section burst switch controller where it separates out
the frame information and performs de-encryption and de-scrambling as required. It then goes to the DSP section where it is
turned back into analog audio. This is amplified by the analog front end, and goes to the TEL LINE Interface.
20.5. Pulse Dialing
During pulse dialing the hookswitch (Q2,Q3) is used to generate the pulses using the HOOK control signal, which is set high
during pulses. To force the line impedance low during the "pause" intervals between dialpulses, the PULSE_DIAL signal turns
on Q7.
during pulses. To force the line impedance low during the "pause" intervals between dialpulses, the PULSE_DIAL signal turns
on Q7.
58
KX-TCD420RUT / KX-A142RUT
21 BLOCK DIAGRAM (HANDSET)
33
CPU
IC3
BBIC
IC1
A/D
D/A
Analog
Front
End
Front
End
Speech
Encoding
Encoding
Speech
Decoding
Decoding
DSP
ADPCM
Codec
Filter
Codec
Filter
BMC
RF
Interface
Interface
MIC
EEPROM
IC2
SDA
SCL
66
67
5
6
SYRI
RSSI
SYEN
RXDA
TXDA
16
12
48
23
13
RF
Module
Module
ANT
BATTERY
TERMINAL
TERMINAL
TP3
TP4
CHARGE
CIRCUIT
Q2
CHARGE
CHARGE DETECT
SWITCHED
SUPPLY
Q1
CHARGE
CONTACTS
CONTACTS
TP5
4.0V
VDDBAT
VDDLR
SWITCH
31
XTAL
10.368
MHz
KEYPAD
COLUMNS
ROWS
LCD
14 Seg
Display
14 Seg
Display
ON SWITCH
38
27
26
36
37
28
2, 5~9
COM 0~5
segment 0~29
1, 87
EARPIECE
42
41
45
17~21
53~55, 59, 60
34
Burst
Encoding
Encoding
Burst
Decoding
Decoding
+
TP6
D3
X1
90~100
72~76
78~84
61, 62, 56~58
72~76
78~84
61, 62, 56~58
KX-A142RUT BLOCK DIAGRAM (HANDSET)
59
KX-TCD420RUT / KX-A142RUT
22 CIRCUIT OPERATION (HANDSET)
22.1. Outline
Handset consists of the following ICs as shown in BLOCK DIAGRAM (HANDSET) (P.59).
·
DECT BBIC (Base Band IC): IC1
−
−
−
−
All data signals (forming/analyzing ACK or CMD signal)
−
−
−
−
All interfaces (ex: Key, Detector Circuit, Charge, DC/DC Converter, EEPROM, LCD)
·
RF Module: IC3
−
−
−
−
PLL Oscillator
−
−
−
−
Detector
−
−
−
−
Compress/Expander
−
−
−
−
Amplifier for transmission and reception
22.2. Power Supply Circuit/Reset Circuit
Circuit Operation:
When power on the Handset, the voltage is as follows;
BATTERY(2.2 V ~ 2.6V: TP3)
→
TP14(4V)
→
IC3(6, 27), D3
→
IC1(37)
→
IC1(39, 63) (2.65V)
The Reset signal generates R19, C23 and 2.65V.
22.3. Charge Circuit
Circuit Operation:
·
When charging the handset on the Base Unit, the charge current is as follows;
DC+(5.5V ~ 6V)
→
D4
→
R43, R44
→
CHARGE+(Base)
→
CHARGE+(Handset)
→
L4
→
Q2
→
F1
→
BATTERY+ ... Battery
... BATTERY-
→
R21
→
GND
→
L5
→
CHARGE-(Handset)
→
CHARGE-(Base)
→
GND
→
DC-(GND)
·
When charging the handset on the Charger Unit, the charge current is as follows;
DC+(5.5V ~ 6V)
→
D1
→
R1, R2
→
CHARGE+(Charger Unit)
→
CHARGE+(Handset)
→
F1
→
BATTERY+ ... Battery ...
BATTERY-
→
R21
→
GND
→
CHARGE-(Handset)
→
CHARGE-(Charger Unit)
→
GND
→
DC-(GND)
In this way, the BBIC on Handset detects the fact that the battery is charged.
The charge current is controlled by switching Q2 of Handset.
Refer to Fig.101 in Power Supply Circuit (P.57).
22.4. Battery Low/Power Down Detector
Circuit Operation:
"Battery Low" and "Power Down" are detected by BBIC which check the voltage from battery.
The detected voltage is as follows;
·
Battery Low
Battery voltage: V(Batt) < 2.3V
The BBIC detects this level and "
" starts flashing and "battery alarm" starts ringing.
·
Power Down
Battery voltage: V(Batt) < 2.2V
The BBIC detects this level and power down.
60
KX-TCD420RUT / KX-A142RUT
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