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7

KX-TG8205/8206  BLOCK DIA

GRAM 

(BASE UNIT)

Analog

Front

End

To TEL_LINE

A

B

CN1

Bridge

Rect

 D3 D3

Hook Switch

Q

4

,Q

5

Audio

Bell/Caller ID

Interface

Charge

Detector

CPU

59

54

61

52

60

56

55

BELL

HOOK

(Optional)

Off-Hook Line Voltage

64 ADCO

A/D

D/A

ADPCM

Codec Filter

DSP

Speech Encoding

BMC

Burst Encoding

RF

Interface

18

19

TXDA

RXDA

21

20

22

SYCL

SYDA

SYEN

ANT1

ANT2

RF Module

18

16

2

31

21

14

13

12

12

13

XTAL

X

1

10.368

MHz

EEPROM

SCL

SDA

6

5

7

To AC Adaptor

CN2

Limit

Resistor

CHARGE

CONTACT

VUNREG

3.3V

Reg.

IC

1

2.5V

Reg.

Q

9

1.8V

Reg.

Q

8

3.3 V

2.5 V

1.8 V

BBIC

Speech Decoding

Burst Decoding

8

Base unit consists of the following ICs as shown in Block Diagram (Base Unit) (P.7).

• DECT BBIC (Base Band IC): IC7

- Handling all the audio, signal and data processing needed in a DECT base unit
- Controlling the DECT specific physical layer and radio section (Burst Module Controller section)
- ADPCM code filter for speech encoding and speech decoding (DSP section)
- Echo-cancellation and Echo-suppression (DSP section)
- Any tones (tone, sidetone, ringing tone, etc.) generation (DSP section)
- DTMF receiver (DSP section)
- Clock Generation for RF Module
- ADC, DAC, timer, and power control circuitry
- All interfaces (ex: RF module, EEPROM, LED, Analog Front End, etc.)

• RF Module: IC10

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

• EEPROM: IC5

- Temporary operating parameters (for RF, etc.)

• Additionally,

- Power Supply Circuit (+3.3 V, +2.5 V, +1.8 V output)
- Crystal Circuit (10.368 MHz)
- Charge Circuit
- Telephone Line Interface Circuit

9

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 → Q8 → IC10 (Radio Transceiver) (Digital)

CN2 (+6.5 V) 

→ IC1 → Q9 → IC10 (Radio Transceiver) (Analog)

CN2 (+6.5 V) 

→ IC1 → R125 → IC10 (Power AMP)

• EEPROM (IC5): 

CN2 (+6.5 V) 

→ IC1 → Q9 → IC5

• Charge Contact (TP16): 

CN2 (+6.5 V) 

→ R57 → R56 → R55 → D22 → 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.