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The power is supplied to the DECT BBIC, RF Module, EEPROM and Charge Contact from AC Adaptor (+6.5V) as shown in
Fig.101. The power supply is as follows;

• DECT BBIC (IC7): 

CN2 (+6.5V) 

→ IC1 → Q9 → IC7

CN2 (+6.5V) 

→ IC1 → Q8 → IC7

• RF Module (IC10): 

CN2 (+6.5V) 

→ IC1 → Q9 → IC10 (PLL)

CN2 (+6.5V) 

→ IC1 → Q10 → IC10 (Power AMP)

• EEPROM (IC5): 

CN2 (+6.5V) 

→ IC1 → Q9 → IC5

• FLASH MEMORY (IC9): 

CN2 (+6.5V) 

→ IC1 → IC9

• TAM Companion (IC8): 

CN2 (+6.5V) 

→ IC1 → Q9 → IC8

CN2 (+6.5V) 

→ IC1 → Q8 → IC8

• Charge Contact (TP16): 

CN2 (+6.5V) 

→ R55, R56 → TP16

<Fig.101>

10

• Bell signal detection
• Clip signal detection
• ON/OFF hook circuit

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)

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]

• Audio Circuits and DTMF tone signal circuits.

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.

*Refer to Signal Route (P.14).

The voice signal input from the TEL LINE interface goes to RF Module (IC10) through DECT BBIC (IC7) as shown in Block Dia-
gram (Base Unit) (P.7)
The voice signal passes through the analog part of IC7 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.
In IC10, 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.

The signal of 1900 MHz band (1881.792 MHz ~ 1897.344 MHz) which is input from antenna is input to IC10 as shown in Block
Diagram (Base Unit) (P.7).
In IC10, the signal of 1900 MHz band is downconverted to 864 kHz signal and demodulated, and goes to IC7 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.

During pulse dialing the hookswitch (Q3, Q4) 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 dial pulses, the PULSE_DIAL signal turns
on Q2.

11

SPEAKER

RECEIVER

MIC

CN4

Headset

CHARGE
CIRCUIT

Q9,Q10,Q11

Q9,Q10,Q11

CHARGE
CONTACTS

CHARGE(+)

CHARGE(-)

CHARGE

CHARGE DETECT

SWITCHED
SUPPLY

   

Q1

Q1

BATTERY

BATTERY+

BATTERY-

TERMINAL

D10

VBAT1

DC/DC-SWITCH

3.0V

Q8

Q8

1.8V

Q7

Q7

4.0V

3.0V

1.8V

LCD

LCD_D/C

LCD_RESET

LCD_CS

WRITE

READ

WRITE

READ

CPU

Analog

Front

End

D/A

A/D

112

5

8

110

111
118

97

96

 107

93

  104 

 105

61

81

ADPCM

Codec

Filter

DSP

Speech

Decoding

Speech

Encoding

BMC

Burst

Decoding

Burst

Encoding

RF

Interface

RF

Module

26

28

RXDA

TXDA

25

38

39

40

RSSI

SYDA
SYEN
SYCL

20

21

XTAL

X1

X1

10.368
MHz

BATTERY

95

ON SWITCH

KEYPAD

ROWS

COLUMNS

57,58,62

50,51,52,53,54,80,83,84

BBIC

 11

LCD-BACK  LIGHT

KEY-BACK  LIGHT

Ringer LED

SRAM_CS

Flash_CS

SRAM

79

42

44 43

59

13

60

1
2
3
4
5

KX-TGA910 BLOCK DIAGRAM (HANDSET)

SP AMP

_

DATA BUS

ADDRESS BUS

ADDRESS BUS:  3~9, 29~35, 122~128

DATA BUS:  68~75, 85~92

Flash ROM

12

Handset consists of the following ICs as shown in Block Diagram (Handset) (P.11).

• 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, Flash ROM, SRAM, LCD)

• FLASH MEMORY (substitute EEPROM): IC2

- Source program data and temporary user data are stored

• SRAM:  IC3

- Application data and code are temporary stored

• RF Module: IC20

- PLL Oscillator
- Detector
- Compress/Expander
- Amplifier for transmission and reception

When power on the Handset, the voltage is as follows;
BATTERY(2.2 V ~ 2.6 V: BAT+) 

→ F1, L1, D1 → Q7 (1.8 V), Q8 (3.0 V), Q1 (4.0 V)

The Reset signal generates IC1 (120 pin) and 1.8 V.

When charging the handset on the Base Unit, the charge current is as follows;
DC+(6.5V) 

→ R55, R56 → CHARGE+(Base) → CHARGE+(Handset) → Q10 → D10 → F1 → BAT+ ... Battery ... 

BAT- 

→ R43 → GND → CHARGE-(Handset)→ CHARGE-(Base) → 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 Q10 of Handset.
Refer to Fig.101 in Power Supply Circuit (P.9).

“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)   2.25V ± 50mV (When the back light disappeares)
The BBIC detects this level and “ ” starts flashing.

• Power Down

Battery voltage: V (Batt)   2.00V ~ 2.05V
The BBIC detects this level and power down.

The hands-free loudspeaker at SP+ and SP- works as a ringer/alarm as well.