Panasonic KX-TG7120FXS, Service Manual, Page: 9 / 90

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KX-TG7120BXS/KX-TG7120BXT/KX-TGA711CXS/KX-TGA711CXT
4.2.2. Power Supply Circuit
The power is supplied to the DECT BBIC, RF Module, EEPROM and Charge Contact from AC Adaptor (+6.5 V) as shown in
Fig.101. The power supply is as follows;
• DECT BBIC (IC7):
CN2 (+6.5 V)
→
IC1
→
Q9
→
IC7
CN2 (+6.5 V)
→
IC1
→
Q8
→
IC7
• RF Module (IC10):
CN2 (+6.5 V)
→
IC1
→
Q9
→
IC10 (PLL)
CN2 (+6.5 V)
→
IC1
→
Q10
→
IC10 (Power AMP)
• EEPROM (IC5):
CN2 (+6.5 V)
→
IC1
→
Q9
→
IC5
• FLASH MEMORY (IC9):
CN2 (+6.5 V)
→
IC1
→
IC9
• TAM Companion (IC8):
CN2 (+6.5 V)
→
IC1
→
Q9
→
IC8
CN2 (+6.5 V)
→
IC1
→
Q8
→
IC8
• Charge Contact (TP16):
CN2 (+6.5 V)
→
R55, R56
→
TP16
<Fig.101>
4.2.3. Telephone Line Interface
<Function>
• Bell signal detection
• Clip signal detection
• ON/OFF hook circuit
Bell & Clip (: Calling Line Identification Presentation: Caller ID) signal detection:
In the standby mode, Q3 is open to cut the DC loop current and decrease the ring load.
When ring voltage appears at the L1T (A) and L1R (B) leads (when the telephone rings), the AC ring voltage is transferred as
follows;
• A
→
C4
→
R6
→
R33
→
IC7 Pin 60 (CID INp)
• B
→
C3
→
R4
→
R35
→
IC7 Pin 52 (CID INn)
ON/OFF hook circuit:
In the standby mode, Q3 is open, and connected as to cut the DC loop current and to cut the voice signal. The unit is conse-
quently in an
on-hook condition .
When IC7 detects a ring signal or press the TALK Key onto the handset, Q4 turns on and then Q3 turns on, thus providing an
off-hook condition (DC current flows through the circuit) and the following signal flow makes the loop current.
• A
→
D3
→
Q3
→
Q5
→
R21
→
R22
→
D3
→
B [ OFF HOOK ]