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13

• Bell signal detection
• ON/OFF hook and pulse dial circuit
• Side tone circuit

In the idle mode, Q141 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 voltage is transferred as follows:
T 

 R111  C110  Q111  BBIC pin 5 [BELL]

When the CPU (BBIC) detects a ring signal, Q141 turns on, thus providing an off-hook condition (active DC current flow through
the circuit). Following signal flow is the DC current flow.
T 

 D101  Q141  Q161  R163  D101  P101  R

Q141 is open, Q141 is connected as to cut the DC loop current and to cut the voice signal. The unit is consequently in an on-
hook condition.

Pin 6 of BBIC turns Q141 ON/OFF to make the pulse dialing.

Basically this circuit prevents the TX signal from feeding back to RX signal. As for this unit, TX signal feed back from Q161 is
canceled by the canceller circuit of BBIC.

• 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.17).

HOOK
BELL

PULSE_MUTE

HOOK

BELL

C120

1000p

RA151

1k

1

2

3

4

C121

680p

C122

680p

C102 680p

C115

100n

C181

NC

R123

NC

(3216)

R158

4.7k

R141

100k

R142

2.7k

(3216)

D141

.

R118

100k

SA101

270V

2

1

R167

NC

R103

NC

C184

1u

P101

C161

10u

*Q141

B

E

C

*C143

1u

Q161

B

C

E

L1R

C103

NC

C164

0.1u

R163

39

(0.5W)

C142

K0.01u

*R149

680

L2R

D142

NC

R117

100k

GAP

1

2

0

6

1

R

0

7

2

D101

1

4

3

2

*Q140

.

L2T

R10

4

NC

R115

5.6M

D133

L1T

C152

0.01u

C104

NC

D132

4

6

1

R

k

2

.

2

R152

130k

Q142

*R148

10k

R165

27k

C101 680p

R144

NC

R162

NC

R151

100k

C167

2700p

SA102

NC

2

1

*R124

10

(3216)

R116

5.6M

C166

NC

C116

100n

C112

0.1u

C110

0.1u

R113

22k

R114

68k

+3.0V

D113

R111

1M

Q111

R112

47k

C113

0.01u

VDDC

C178

0.1u

C193

0.027u

C175

560p

+3.0V

Q171

R171

220

R172

680k

R176

1k

R175

3.9k

R177

1k

C176

1u

C171

0.033u

*C141

2.2u

R159

1.5k

*R145

3.9k

R169

47k

R121

390k

R122

390k

D143

NC

L101

27n

RX

(BLACK)

(BROWN)

(RED)

(YELLOW)

Bell detection

DC Monitor

Caller ID

TX

Pin 16 of IC501

Pin 28of IC501

Pin 24 of IC501

Pin 25 of IC501

Pin 5 of IC501

Pin 6 of IC501

Pin 17 of IC501

Pin 19 of IC501

Pin 18 of IC501

14

The voice signal input from the TEL LINE interface goes to DECT BBIC (IC501) as shown in  Block Diagram (Base
Unit_Main)(P.8)
The voice signal passes through the analog part of IC501 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 IC501, the carrier frequency is changing, and frequency modulated RF signal is generated.In IC501,RF signal is 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 IC501 as shown in  Block
Diagram (Base Unit_Main)(P.8).
In IC501, the signal of 1900 MHz band is downconverted to 864 kHz signal and demodulated, 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 dialling the hookswitch (Q141, Q142) 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 Q140.

15

QSPI

FLASH MEMORY

IC4

Reset

Reset

P

in 71

SPEAKER

RECEIVER

MIC

CHARGE

CIRCUIT

Q2, Q3, Q4,

Q9, R8

CHARGE

CONTACTS

CHARGE(+)

CHARGE_CTRL

CHARGE_DET

EEPROM

SCL

SDA

BATTERY

TERMINAL

R45

VBAT

BATT-

1.8 V

Q1

1.8 V

LCD

CD

RESET

CS

SID

 SCL

CPU

Analog

Front

End

D/A

A/D

35

37

21

22

17

18

34

33

66

67

 32

24

44

45

73

63

64

77

76

ADPCM

Codec

Filter

DSP

Speech

Decoding

Speech

Encoding

BMC

Burst

Decoding

ANT1

Burst

Encoding

RF

PLL

MOD/DEMOD

1

2

87

86

RXn

ANT1

RXp

TXp

TXn

7

8

XTAL

X1

10.368

MHz

BATTERY

46

ON SWITCH

KEYPAD

Charge

Pump

ROWS

COLUMNS

CP3V

CP4V

57, 58, 59, 60

11, 12, 13, 14, 25, 55

47, 48, 51, 53 QSPI-IO 0-3

BBIC

 65

LC

D

-BA

CK  LIGHT

KEY LED

61

LDO_CTRL

1.8 V

CP3V

QSPI

Control

52 QSPI-SCK

49 QSPI-

CS

CP 3V

 L

CD_LED0

CP4V

CP3V

1.8 V

GND

16

Handset consists of the following ICs as shown in Block Diagram (Handset) (P.15).

• 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, EEPROM, LCD, RF Power Amp.)
- PLL Oscillator
- Detector
- Compress/Expander
- Reception
- Integrated 1.9 GHz PA for DECT

• QSPI FLASH MEMORY: IC4

- Main Program D/L Area

• EEPROM: IC7

Following information data is stored

- Settings

ex: ID code, user setting

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

 Q1 (1.8 V), IC1-44pin (CP3V)

The Reset signal generates IC1 (71 pin) and 1.8 V.

When charging the handset on the Base Unit, the charge current is as follows;

DC+(5.5 V) 

 R371  R372  D362  CHARGE+(Base)  CHARGE+(Handset)  

 

 Q3  BATTERY+... Battery... 

BATTERY- 

 R45  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 Q9 of Handset.
Refer to Fig.101 in Power Supply Circuit/Reset Circuit (P.16).

“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)   2.25 V ± 50 mV

The BBIC detects this level and "

" starts flashing.

• Power Down

Battery voltage: V(Batt)   2.0 V ± 50 mV
The BBIC detects this level and power down.

The hands-free loudspeaker at SP+ and SP- is used to generate the ring alarm.

1.8V

Battery +

Reset 
(IC1_71 pin)

Q2
R8