Panasonic KX-TC1019RUB Service Manual ▷ View online
20 CIRCUIT OPERATION (BASE UNIT)
20.1. TELEPHONE LINE INTERFACE
20.1.1. Circuit operation (ON HOOK MODE):
Q102 is open; it is connected for cutting the DC loop current and the voice signal. The unit is consequently in an ON-HOOK
condition.
condition.
In the ON-HOOK state (idle), Ring signal flows as follows:
TIP
TIP
→
P101
→
L101
→
R101
→
C101
→
Q101B
→
Q101E
→
C102
→
R102
→
L102
→
RING
The 48V DC component is blocked by C101, C102, thereby providing an ON-HOOK condition.
20.2. TELEPHONE MODE OPERATION
20.2.1. Circuit Operation:
1. When a ring signal enters from the Line, the ring detection circuit (Transistor Q101) begins to operate, so Q101 turns on, thus
input a low level to the BELL pin 55 of the IC601 (CPU).
2. To show the arrival of the ring signal to the portable unit, Pin 17 of IC601 enters into the transmit mode and becomes High level.
The ring data, having the code set by Pin 21 of IC601 is sent to the portable unit as a frequency modulated output signal.
3. When receiving the ring signal, and the user presses the talk button to switch from standby to the talk mode, the base unit
receives the modulated data from the portable unit, which includes the information that the portable unit becomes from
“Standby” to “Talk”. This data is then demodulated at the base unit and passes through a data signal amplifier of IC801.
“Standby” to “Talk”. This data is then demodulated at the base unit and passes through a data signal amplifier of IC801.
This signal is then input to Pin 22 of IC601, which causes Q102 and Q103 to switch “ON” and make the DC loop of telephone
line interface.
line interface.
4. Pin 18 of IC601 becomes LOW (LOW level voltage)and the IN USE LED (LED601) is on.
<Fig 101>
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KX-TC1019RUB
20.3. TRANSMITTER CIRCUIT
The voice signal or the data signal sent to the portable unit is applied in the anode of the variable capacitor diode (VARICAP) D851.
The capacitance of VARICAP is changing in accordance with the Voice signal or Tx DATA signal. Therefore, the carrier frequency
which is generated by IC802 and L851 will be changing, and Frequency modulated RF signal is generated. Then, amplified by
IC802 - Amplifier part, pass through the duplexer, and radiated from Antenna.
The capacitance of VARICAP is changing in accordance with the Voice signal or Tx DATA signal. Therefore, the carrier frequency
which is generated by IC802 and L851 will be changing, and Frequency modulated RF signal is generated. Then, amplified by
IC802 - Amplifier part, pass through the duplexer, and radiated from Antenna.
<Fig 102>
20.4. TRANSMITTER SIGNAL CIRCUIT
20.4.1. Circuit Operation:
1. The signal input from the TEL LINE goes through Telephone line interface to R701
→
C702
→
Q701B
→
Q701C
→
C704
→
VR701
→
C706
→
R707
→
R708
→
C828
→
R817 and it is input to the signal amplifier of IC801, pin 9.
This amplifier includes the limiter circuit. And signal goes through the compressor and SPLATTER FILTER, it is output from the
pin 3 of IC801. Then it goes out to the transmitter circuit. R819
pin 3 of IC801. Then it goes out to the transmitter circuit. R819
→
R851
→
C852
→
R853
→
D851
<Fig 103>
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KX-TC1019RUB
20.5. Receiver RF IF Circuit
20.5.1. Circuit Operation:
The signal of 40MHz band (39.775~40.000MHz) which is input from ANT is filtered at DUP801, then it is input to Pin 41 of
IC801. 1st local frequency is decided by the serial data which is output from Pin 9, 10 and 12 of IC601 and controlled by phase
lock-loop system (PLL). PLL system is constructed by RX VCO (T801), RX PLL and LPF. RX VCO which oscillates at T801 and
Pins 44, 45 of IC 801 is input to programmable controller at inside of IC801.
The input signal, Pin 41 of IC801 and 1st local frequency output from RX VCO are mixed at inside of IC801. The phase-detector
signal that indicates the difference between the current oscillation frequency and the desired one is feed backed to the voltage
controlled oscillator. Then the frequency difference is reduced and finally locked to the desired frequency (1st local one). Also
1st local frequency is mixed with the received RF signal. Then it passes through CF801, and 1st IF frequency of 10.695MHz
is generated. Further,11.15MHz which is oscillated at X801 and Pins 52, 53 of IC801 are mixed at inside of IC801 and filtered
at CF802, and 2nd IF 450kHz is output.
IC801. 1st local frequency is decided by the serial data which is output from Pin 9, 10 and 12 of IC601 and controlled by phase
lock-loop system (PLL). PLL system is constructed by RX VCO (T801), RX PLL and LPF. RX VCO which oscillates at T801 and
Pins 44, 45 of IC 801 is input to programmable controller at inside of IC801.
The input signal, Pin 41 of IC801 and 1st local frequency output from RX VCO are mixed at inside of IC801. The phase-detector
signal that indicates the difference between the current oscillation frequency and the desired one is feed backed to the voltage
controlled oscillator. Then the frequency difference is reduced and finally locked to the desired frequency (1st local one). Also
1st local frequency is mixed with the received RF signal. Then it passes through CF801, and 1st IF frequency of 10.695MHz
is generated. Further,11.15MHz which is oscillated at X801 and Pins 52, 53 of IC801 are mixed at inside of IC801 and filtered
at CF802, and 2nd IF 450kHz is output.
<Fig 104>
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KX-TC1019RUB
20.6. RECEIVER SIGNAL CIRCUIT
20.6.1. Circuit Operation:
1. The detected signal passes through R806
→
C815
→
R807 and it is input to the Pre Amplifier inside of IC801; it passes through
the expander and goes out from pin 21 of IC801.
2. The signal passes through C822
→
R811 and it is input to the Line Amplifier of IC801, on pin 17 .
3. The signal is output from the amplifier on pin 16 of IC801 and it goes through C710, R714 and R709 to the telephone line.
<Fig 105>
20.6.2. Explanation of the Data Reception Circuit of Base Unit
<Fig 106>
In the area where the transmission power from the portable unit is extremely weak, the noise is superimposed on the data and
the chance of an error can become extremely great upon reception of the data. To help prevent this, the above circuit is used.
Demodulated signal is filtered by R809 and C820. The data signal is made square shape by data limitting AMP. RX Data is
output from pin 13 of IC801 and supplied to pin 22 of IC601 via CN802, R612.
the chance of an error can become extremely great upon reception of the data. To help prevent this, the above circuit is used.
Demodulated signal is filtered by R809 and C820. The data signal is made square shape by data limitting AMP. RX Data is
output from pin 13 of IC801 and supplied to pin 22 of IC601 via CN802, R612.
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KX-TC1019RUB
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