Panasonic KX-TC1205RUB / KX-TC1205RUW / KX-TC1205RUS / KX-TC1205RUF Service Manual ▷ View online
16.4. Charge Circuit
Circuit Operation:
When charging the handset on the base unit, the charge current is as follows;
DC (JK2)
→
L8
→
D6
→
L7
→
CHG+(Base)
→
[CHG+(Handset)
→
L4
→
Q9
→
BATT(1)....Battery....BATT(2)
→
L5
→
CHG-(Handset)]
→
CHG+(Base)
→
L5,
In this way, the CPU on both unit detects the fact that the battery is charged.
The charge current is controlled by switching Q701 of Handset. The battery is charged in normal mode for 10 hours and then
in trickle mode.
in trickle mode.
16.5. Telephone Line Interface
Function:
•
•
Bell signal detection
•
•
ON/OFF hook and pulse dial circuit
•
•
Side tone circuit
Bell signal detection and OFF HOOK circuit:
In the idle mode, Q103 is open to cut the DC loop current and decrease the ring load. When ring voltage appears at the Tip (T)
and Ring (R) leads (when the telephone rings), the AC ring volltage is transferred as follows.
and Ring (R) leads (when the telephone rings), the AC ring volltage is transferred as follows.
JK1 (3): T
→
L6
→
R144
→
IC3D (12,13
→
14)
→
C97
→
R148
→
Q20
→
IC2 (24) [BELL]
JK1 (2): R
→
L4
→
R120
→
R152
→↑
When the CPU (DSP) detects a ring signal and press the TALK Key on the handset. Q6 turns on and then RY1 turns on, thus
providing an off-hook condition (active DC current flow through the circuit) and the following singal flow is for the loop current.
providing an off-hook condition (active DC current flow through the circuit) and the following singal flow is for the loop current.
T
→
R160
→
L4
→
RY1
→
R107
→
T7
→
R116
→
D5
→
L6
→
R161
→
R [OFF HOOK]
ON HOOK Circuit:
Q6 is open, RY1 disconnected as to cut the DC loop current and to cut the voice signal. The unit is consequently in an on-hook
condition.
condition.
Pulse Dial Circuit:
DSP (Relay) turns RY1 ON/OFF to make the pulse dialing via Q6.
Make/Break ratio when dialing with the Handset: 40%:60%
Side Tone Circuit:
Basically this circuit prevents the TX signal from feeding back to RX signal.
As for this unit, TX signal feed back from Q11 is canceled by the cancellor circuit of AGC.
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KX-TC1205RUB / KX-TC1205R UW / KX-TC1205R US / KX-TC1205RUF
16.6. Transmitter/Receiver
Base Unit and Handset are mainly consists of RF(Radio Frequency) IC and CPU.
Base Unit and Handset transmit/receive voice signal and data signal through the antenna on carrier frequency.
Signal Pass :
*Refer to CDL TX/RX in Signal Route (P.44).
16.6.1. Base to Handset
Circuit Operation:
The voice signal input from the TEL LINE interface goes to RF IC as shown in
BLOCK DIAGRAM (BASE UNIT) (P.36).
In the talk mode (off-hook) condition, the telephone line voice signal passes through D2, D3, D4, D5, RY1 (Relay), R107 and
T7.
T7.
The other party´s voice signal is coupled with T7 and amplified by Q11 and led to IC3-B (OP Amplifier device).
And the signal goes through the compressor of RF IC, it is output to transmitter circuit.
The signal of the data sent to the handset is applied in the anode of the variable capacitor diode (VARICAP : DV1).
The capacitor of VARICAP is changing in accordance with the voice signal from telephone line interface or TX DATA signal from
CPU.
CPU.
Therefore, the carrier frequency which is generated by TXVCO will be changing, and Frequency modulated RF signal is
generated and amplified by RF AMP(Q3, Q4, T5).
generated and amplified by RF AMP(Q3, Q4, T5).
It pass through the Duplexer DPX1 and radiated from Antenna.
The signal is transmitted from the base unit and received by the handset antenna and amplified by RF amplifier (Q1) through
DPX1 as shown in BLOCK DIAGRAM (HANDSET) (P.37). And then it is converted to 10.7 MHz and 450 KHz Intermediate
frequency by RF IC and related components.
frequency by RF IC and related components.
The demodulated audio signal is output from RF IC (DET OUT) and passed through "Expander" process to reduce noise, then
voice signal amplified by "Receiver amplifier" is output to receiver (REC1).
voice signal amplified by "Receiver amplifier" is output to receiver (REC1).
The receiver loudness is adjustable using "LOUD" key on the handset. Q2 and Q3 control the volume. When CPU (VOL1)
becomes low, the volume becomes “MID”, while CPU (VOL 1,2) becomes low, the volume becomes "HIGH".
becomes low, the volume becomes “MID”, while CPU (VOL 1,2) becomes low, the volume becomes "HIGH".
TX data (to Handset)
CPU (VTX) becomes low to turn on the transmission power transistor Q2, and CPU (TX-data) sends data signal. It is FM-
modulated by TXVCO and driven by RF AMP, then transmitted to the handset.
modulated by TXVCO and driven by RF AMP, then transmitted to the handset.
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KX-TC1205RUB / KX-TC1205R UW / KX-TC1205R US / KX-TC1205RUF
16.6.2. Handset to Base
Circuit Operation:
The voice signal from the handset user is picked up by the microphone (MC1), voice signal passes through "Compressor"
process to reduce noise as shown in BLOCK DIAGRAM (HANDSET) (P.37). And the voice is FM-modulated by VARICAP
(DV1).
(DV1).
The carrier frequency is generated by TX VCO. The transmitter power transistor Q4 is turned on/off by CPU (VTX).
The carrier signal is amplified by RF AMP and sent to the handset duplexer and antenna.
The signal of 49MHz band (49.670~49.99MHz) which is input from ANT is filtered at DPX1 as shown in
BLOCK DIAGRAM (BASE UNIT) (P.36), then it is input to RF IC.
The signal input to RF IC is converted through Mixer inside of RF IC, RF filter (CF1, CF2) and Expander.
The signal is transmitted from the handset and received by the base unit antenna and amplified by RF amplifier Q1, then it is
converted to10.7 MHz and 450 KHz Intermediate by RF IC. The demodulated audio signal is output from RF IC (DET OUT) and
passed through "Expander" process to reduce noise, then voice signal is led to LINE AMP.
converted to10.7 MHz and 450 KHz Intermediate by RF IC. The demodulated audio signal is output from RF IC (DET OUT) and
passed through "Expander" process to reduce noise, then voice signal is led to LINE AMP.
The signal is passed through TELEPHONE INTERFACE and Tel-line.
RX data (from Handset):
The data signal from handset (ex: Talk, ACK, COM) is also included in 49 MHz band same as the voice data. After second if
filter, the data signal is made square shape by data limiting AMP of the RF IC. RX data is output to CPU (RX Data).
filter, the data signal is made square shape by data limiting AMP of the RF IC. RX data is output to CPU (RX Data).
16.6.3. RF signal operation/control and PLL operation (RF UNIT)
Base unit radio frequency signal received by antenna passes through duplexer (DPX1). RF signal is amplified by RF AMP.
RF signal received from RF IC is mixed with RX local frequency at Mixer to generate 10.7 MHz wide band IF. The reference
frequency is generated by X1 11.15 MHz crystal.
frequency is generated by X1 11.15 MHz crystal.
VC1 is the reference frequency for adjustment. The 10.7 MHz is mixed with reference and 450KHz narrow band IF is generated.
The demodulation audio signal is adjusted to the maximum at T1.
The demodulation audio signal is adjusted to the maximum at T1.
RF IC is controlled by CPU (RF_STB, DATA, CLK). The RX local frequency is generated by RXVCO.
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KX-TC1205RUB / KX-TC1205R UW / KX-TC1205R US / KX-TC1205RUF
16.7. Signal Route
Each signal route is as follows.
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KX-TC1205RUB / KX-TC1205R UW / KX-TC1205R US / KX-TC1205RUF
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