Panasonic KX-TCD400RUB / KX-TCD400RUC / KX-TCD400RUF / KX-A140RUB / KX-A140RUC / KX-A140RUF Service Manual ▷ View online
20 CIRCUIT OPERATION (BASE UNIT)
20.1. Outline
Base Unit consists of the following ICs as shown in BLOCK DIAGRAM (BASE UNIT) (P.48).
·
DECT BBIC (Base Band IC): IC2
−
−
Handling all the audio,signal and data processing needed in a DECT base unit
−
−
Controlling the DECT specific physical layer and radio section (Burst Module Controller section)
−
−
ADPCM codec filter for speech encoding and speech decoding (DSP section)
−
−
Echo-cancellation and Echo-suppression (DSP section)
−
−
Any tones (tone,sidetone,ringing tone,etc.) generation (DSP section)
−
−
DTMF receiver (DSP section)
−
−
Clock Generation for RF Module
−
−
ADC,DAC,timer,and power control circuitry
−
−
All interfaces (ex: RF module,EEPROM,LED,Analog Front End,etc.)
·
RF Module: IC3
−
−
PLL Oscillator
−
−
Detector
−
−
Compress/Expander
−
−
First/Second Mixer
−
−
Amplifier for transmission and reception
·
EEPROM: IC1
−
−
Temporary operating parameters (for RF,etc.)
·
Additionally,
−
−
Power Supply Circuit (+4.0V,+2.65V output)
−
−
Crystal Circuit (10.368MHz)
−
−
Charge Circuit
−
−
Telephone Line Interface Circuit
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KX-TCD400RUB / KX-TCD400RUC / KX-TCD400RUF / KX-A140RUB / KX-A140RUC / KX-A140RUF
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 (IC2): J2(+6V)
→
D4
→
Q9
→
D5
→
Q8
→
IC2
·
RF Module (IC3): J2(+6V)
→
D4
→
Q9
→
IC3
·
EEPROM (IC1): J2(+6V)
→
D4
→
Q9
→
D5
→
Q8
→
IC2
→
IC1
·
LED (LED1): J2(+6V)
→
D4
→
Q9
→
R68
→
LED1
·
Charge Contact (TP84): J2(+6V)
→
D4
→
R43,R44
→
TP84
<Fig.101>
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KX-TCD400RUB / KX-TCD400RUC / KX-TCD400RUF / KX-A140RUB / KX-A140RUC / KX-A140RUF
20.3. Telephone Line Interface
<Function>
·
Bell signal detection
·
ON/OFF hook circuit
·
Audio circuits
Bell 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;
When ring voltage appears at the TP3 (A) and TP40 (B) leads (when the telephone rings),the signal is transferred as follows;
·
A
→
C4
→
R2
→
R29
→
IC2 (DLP) [BELL]
·
B
→
C3
→
R1
→
R30
→
IC2 (DLP) [BELL]
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.
When IC2 detects a ring signal or press the TALK Key onto the handset,Q3 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.
consequently in an off-hook condition.
When IC2 detects a ring signal or press the TALK Key onto the handset,Q3 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.
·
A
→
R77
→
D2
→
Q2
→
R8
→
Q3
→
D2
→
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.
Base Unit and Handset transmit/receive voice signal and data signal through the antenna on carrier frequency.
Signal Pass:
*Refer to SIGNAL ROUTE (P.54).
20.4.1. Transmitter Block
The voice signal input from the TEL LINE interface goes to RF Module (IC3) through DECT BBIC (IC2) as shown in BLOCK
DIAGRAM (BASE UNIT) (P.48)
The voice signal passes through the analog part of IC2 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
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.
DIAGRAM (BASE UNIT) (P.48)
The voice signal passes through the analog part of IC2 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
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.
20.4.2. Receiver Block
The signal of 19.2 MHz band (18.81792 MHz ~ 18.97344 MHz) which is input from antenna is input to IC3 as shown in BLOCK
DIAGRAM (BASE UNIT) (P.48).
In IC3,the signal of 19.2 MHz band is downconverted to 864 kHz signal and demoduleted,and goes to IC2 as 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.
DIAGRAM (BASE UNIT) (P.48).
In IC3,the signal of 19.2 MHz band is downconverted to 864 kHz signal and demoduleted,and goes to IC2 as 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.
51
KX-TCD400RUB / KX-TCD400RUC / KX-TCD400RUF / KX-A140RUB / KX-A140RUC / KX-A140RUF
21 BLOCK DIAGRAM (HANDSET)
KX-A140RUB/RUC/RUF 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
52
KX-TCD400RUB / KX-TCD400RUC / KX-TCD400RUF / KX-A140RUB / KX-A140RUC / KX-A140RUF
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