Panasonic KX-TG6841B User manual

© Panasonic System Networks Co., Ltd. 2013
Unauthorized copying and distribution is a violation
of law.
ORDER NO. KM41302656CE
F13
Telephone Equipment
Model No. KX-TG6841B
KX-TG6842B
KX-TG6843B
KX-TG6844B
KX-TG6845B
KX-TG6873B
KX-TGA680B
KX-TGA20B
Digital Cordless Answering System
B: Black Version
(for U.S.A.)
(Handset)
KX-TGA680 KX-TG6841/6871
(Base Unit)
KX-TGA20
(Charger Unit)
Model No
Base Unit Handset Charger Unit Key detector Expandable
KX-TG6841 1 (TG6841) 1 (TGA680) Up to 6
KX-TG6842
1 (TG6841) 2 (TGA680) 1 Up to 6
KX-TG6843
1 (TG6841) 3 (TGA680) 2 Up to 6
KX-TG6844
1 (TG6841) 4 (TGA680) 3 Up to 6
KX-TG6845
1 (TG6841) 5 (TGA680) 4 Up to 6
KX-TG6873
1 (TG6841) 3 (TGA680) 2 1 Up to 6
KX-TGA680*
1 (TGA680) 1
Configuration for each model
(Key detector KX-TG6873 only)
*KX-TGA680 is also an optional accessory, which contains a
handset and a charger.

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KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
WARNING
This service information is designed for experienced repair technicians only and is not designed for use by the general
public. It does not contain warnings or cautions to advise non-technical individuals of potential dangers in attempting
to service a product. Products powered by electricity should be serviced or repaired only by experienced professional
technicians. Any attempt to service or repair the product or products dealt with in this service information by anyone
else could result in serious injury or death.
IMPORTANT SAFETY NOTICE
There are special components used in this equipment which are important for safety. These parts are marked by
in the Schematic Diagrams, Circuit Board Diagrams, Exploded Views and Replacement Parts List. It is essential that
these critical parts should be replaced with manufacturer’s specified parts to prevent shock, fire or other hazards.
Do not modify the original design without permission of manufacturer.
IMPORTANT INFORMATION ABOUT LEAD FREE, (PbF), SOLDERING
If lead free solder was used in the manufacture of this product, the printed circuit boards will be marked PbF.
Standard leaded, (Pb), solder can be used as usual on boards without the PbF mark.
When this mark does appear, please read and follow the special instructions described in this manual on the
use of PbF and how it might be permissible to use Pb solder during service and repair work.
LWhen you note the serial number, write down all 11 digits. The serial number may be found on the bottom of the unit.
LThe illustrations in this Service Manual may vary slightly from the actual product.

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KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
TABLE OF CONTENTS PAGE PAGE
1 Safety Precautions----------------------------------------------- 5
1.1. For Service Technicians --------------------------------- 5
2 Warning-------------------------------------------------------------- 5
2.1. Battery Caution--------------------------------------------- 5
2.2. About Lead Free Solder (PbF: Pb free)-------------- 6
2.2.1. Suggested PbF Solder ------------------------------ 6
2.3. Discarding of P. C. Board-------------------------------- 6
3 Specifications ----------------------------------------------------- 7
4 Technical Descriptions ----------------------------------------- 8
4.1. US-DECT Description------------------------------------ 8
4.1.1. TDD Frame Format ---------------------------------- 8
4.1.2. TDMA system------------------------------------------ 8
4.1.3. Signal Flowchart in the Radio Parts-------------- 9
4.2. Block Diagram (Base Unit_Main)---------------------10
4.3. Block Diagram (Base Unit_RF Part)-----------------11
4.4. Circuit Operation (Base Unit)--------------------------12
4.4.1. BBIC (Base Band IC: IC501) ---------------------12
4.4.2. Flash Memory (IC601)------------------------------12
4.4.3. EEPROM (IC611)------------------------------------12
4.4.4. Power Supply Circuit/Reset Circuit--------------13
4.4.5. Telephone Line Interface---------------------------15
4.4.6. Parallel Connection Detect Circuit/Auto
Disconnect Circuit -----------------------------------16
4.4.7. Calling Line Identification (Caller ID)/Call
Waiting Caller ID-------------------------------------17
4.5. Block Diagram (Handset)-------------------------------19
4.6. Block Diagram (Handset_RF Part)-------------------20
4.7. Circuit Operation (Handset)----------------------------21
4.7.1. Outline--------------------------------------------------21
4.7.2. Power Supply Circuit/Reset Circuit--------------21
4.7.3. Charge Circuit ----------------------------------------22
4.7.4. Battery Low/Power Down Detector--------------22
4.7.5. Speakerphone----------------------------------------22
4.8. Behavior of Electric Power Failure-------------------23
4.9. Circuit Operation (Charger Unit)----------------------23
4.10. Signal Route-----------------------------------------------24
5 Location of Controls and Components ------------------26
6 Installation Instructions---------------------------------------26
7 Operating Instructions-----------------------------------------26
8 Test Mode ----------------------------------------------------------27
8.1. Engineering Mode----------------------------------------27
8.1.1. Base Unit ----------------------------------------------27
8.1.2. Handset ------------------------------------------------29
9 Service Mode -----------------------------------------------------31
9.1. How to Clear User Setting (Handset Only)---------31
10 Troubleshooting Guide----------------------------------------32
10.1. Troubleshooting Flowchart-----------------------------32
10.1.1. Check Power------------------------------------------33
10.1.2. Check Record ----------------------------------------34
10.1.3. Check Playback -------------------------------------37
10.1.4. Check Battery Charge------------------------------37
10.1.5. Check Link---------------------------------------------38
10.1.6. Check the RF part -----------------------------------40
10.1.7. Registering a Handset to the Base Unit--------44
10.1.8. Deregistering a Handset---------------------------44
10.1.9. Check Handset Transmission --------------------45
10.1.10. Check Handset Reception-------------------------45
10.1.11. Check Caller ID --------------------------------------45
11 Disassembly and Assembly Instructions---------------46
11.1. Disassembly Instructions-------------------------------46
11.1.1. Base Unit----------------------------------------------46
11.1.2. Handset------------------------------------------------ 48
11.1.3. Charger Unit------------------------------------------49
11.2. How to Replace the Base Unit LCD-----------------50
11.3. How to Replace the Handset LCD-------------------52
12 Measurements and Adjustments --------------------------53
12.1. Equipment Required ------------------------------------53
12.2. The Setting Method of JIG-----------------------------53
12.2.1. Connections (Base Unit) --------------------------53
12.2.2. Connections (Handset) ----------------------------54
12.2.3. How to install Batch file into P.C.----------------55
12.2.4. Commands (Base Unit)----------------------------56
12.2.5. Commands (Handset)------------------------------56
12.3. Adjustment Standard (Base Unit)--------------------57
12.3.1. Bottom View ------------------------------------------ 57
12.4. Adjustment Standard (Handset)----------------------58
12.4.1. Component View ------------------------------------ 58
12.5. Things to Do after Replacing IC or X'tal------------59
12.5.1. How to download the data ------------------------59
12.6. Frequency Table------------------------------------------61
13 Miscellaneous----------------------------------------------------62
13.1. How to Replace the LLP (Leadless Leadframe
Package) IC ----------------------------------------------- 62
13.1.1. Preparation--------------------------------------------62
13.1.2. Caution-------------------------------------------------62
13.1.3. How to Remove the IC-----------------------------62
13.1.4. How to Install the IC --------------------------------63
13.2. How to Replace the Flat Package IC ---------------64
13.2.1. Preparation--------------------------------------------64
13.2.2. How to Remove the IC-----------------------------64
13.2.3. How to Install the IC --------------------------------65
13.2.4. How to Remove a Solder Bridge---------------- 65
13.3. Terminal Guide of the ICs, Transistors and
Diodes ------------------------------------------------------66
13.3.1. Base Unit----------------------------------------------66
13.3.2. Handset------------------------------------------------ 66
14 Schematic Diagram --------------------------------------------67
14.1. For Schematic Diagram --------------------------------67
14.1.1. Base Unit (Schematic Diagram (Base
Unit_Main)) ------------------------------------------- 67
14.1.2. Handset (Schematic Diagram
(Handset_Main))-------------------------------------67
14.2. Schematic Diagram (Base Unit_Main)--------------68
14.3. Schematic Diagram (Base Unit_Operation)-------70
14.4. Schematic Diagram (Base Unit_LED) --------------71
14.5. Schematic Diagram (Handset_Main) ---------------72
15 Printed Circuit Board ------------------------------------------75
15.1. Circuit Board (Base Unit_Main) ----------------------75
15.1.1. Component View ------------------------------------ 75
15.1.2. Bottom View ------------------------------------------ 76
15.2. Circuit Board (Base Unit_Operation)---------------- 77
15.3. Circuit Board (Base Unit_LED)----------------------- 77
15.4. Circuit Board (Handset_Main) ------------------------79
15.4.1. Component View ------------------------------------ 79
15.4.2. Bottom View ------------------------------------------ 80
16 Exploded View and Replacement Parts List----------- 81

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KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
16.1. Cabinet and Electrical Parts (Base Unit)-----------81
16.2. Cabinet and Electrical Parts (Handset)-------------82
16.3. Cabinet and Electrical Parts (Charger Unit)-------83
16.4. Accessories and Packing Materials -----------------84
16.4.1. KX-TG6841B -----------------------------------------84
16.4.2. KX-TG6842B -----------------------------------------85
16.4.3. KX-TG6843B -----------------------------------------86
16.4.4. KX-TG6844B -----------------------------------------87
16.4.5. KX-TG6845B -----------------------------------------88
16.4.6. KX-TG6873B -----------------------------------------89
16.4.7. KX-TGA680B-----------------------------------------90
16.5. Replacement Parts List---------------------------------91
16.5.1. Base Unit----------------------------------------------91
16.5.2. Handset------------------------------------------------93
16.5.3. Charger Unit ------------------------------------------94
16.5.4. Accessories and Packing Materials-------------94
16.5.5. Screws -------------------------------------------------95
16.5.6. Fixtures and Tools-----------------------------------95

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KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
1 Safety Precautions
1.1. For Service Technicians
•Repair service shall be provided in accordance with repair technology information such as service manual so as to
prevent fires, injury or electric shock, which can be caused by improper repair work.
1. When repair services are provided, neither the products nor their parts or members shall be remodeled.
2. If a lead wire assembly is supplied as a repair part, the lead wire assembly shall be replaced.
3. FASTON terminals shall be plugged straight in and unplugged straight out.
•ICs and LSIs are vulnerable to static electricity.
When repairing, the following precautions will help prevent recurring malfunctions.
1. Cover plastic parts boxes with aluminum foil.
2. Ground the soldering irons.
3. Use a conductive mat on worktable.
4. Do not grasp IC or LSI pins with bare fingers.
2Warning
2.1. Battery Caution
Risk of explosion if battery is replaced by an incorrect type. Dispose of used batteries according to the instructions.
Attention:
A nickel metal hydride battery that is recyclable powers the product you have purchased.
Please call 1-800-8-BATTERY (1-800-822-8837) for information on how to recycle this battery.

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KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
2.2. About Lead Free Solder (PbF: Pb free)
Note:
In the information below, Pb, the symbol for lead in the periodic table of elements, will refer to standard solder or solder that
contains lead.
We will use PbF solder when discussing the lead free solder used in our manufacturing process which is made from Tin (Sn),
Silver (Ag), and Copper (Cu).
This model, and others like it, manufactured using lead free solder will have PbF stamped on the PCB. For service and repair
work we suggest using the same type of solder.
Caution
• PbF solder has a melting point that is 50 °F ~ 70 °F (30 °C ~ 40 °C) higher than Pb solder. Please use a soldering iron with
temperature control and adjust it to 700 °F ± 20 °F (370 °C ± 10 °C).
• Exercise care while using higher temperature soldering irons.:
Do not heat the PCB for too long time in order to prevent solder splash or damage to the PCB.
• PbF solder will tend to splash if it is heated much higher than its melting point, approximately 1100 °F (600 °C).
• When applying PbF solder to double layered boards, please check the component side for excess which may flow onto the
opposite side (See the figure below).
2.2.1. Suggested PbF Solder
There are several types of PbF solder available commercially. While this product is manufactured using Tin, Silver, and Copper
(Sn+Ag+Cu), you can also use Tin and Copper (Sn+Cu), or Tin, Zinc, and Bismuth (Sn+Zn+Bi). Please check the
manufacturer's specific instructions for the melting points of their products and any precautions for using their product with other
materials.
The following lead free (PbF) solder wire sizes are recommended for service of this product: 0.3 mm, 0.6 mm and 1.0 mm.
2.3. Discarding of P. C. Board
When discarding P. C. Board, delete all personal information such as telephone directory and caller list or scrap P. C. Board.
Component
Component
pin
Solder
Remove all of the
excess solder
(Slice View)
0.3 mm X 100 g 0.6 mm X 100 g 1.0 mm X 100 g

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KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
3 Specifications
Note:
• Design and specifications are subject to change without notice.
Note for Service:
•Operation range: Up to 300 m outdoors, Up to 50 m indoors, depending on the condition.
•Analog telephone connection: Telephone Line
•Optional headset: KX-TCA60, KX-TCA93, KX-TCA400, KX-TCA430
•Optional Range extender: KX-TGA405
•Optional Key detector: KX-TGA20
Power source
Receiving Method
Oscillation Method
Detecting Method
Tolerance of OSC Frequency
Modulation Method
ID Code
Ringer Equivalence No. (REN)
Dialing Mode
Redial
Speed Dialer
Power Consumption
Operating Conditions
Dimensions (H x W x D)
Mass (Weight)
AC Adaptor
(PNLV226Z, 120 V AC, 60 Hz)
Super Heterodyne
PLL synthesizer
Quadrature Discriminator
13.824 MHz ±100 Hz
Frequency Modulation
40 bit
0.1B
Tone(DTMF)/Pulse
Up to 48 digits
Up to 24 digits (Phonebook)
Standby: Approx. 0.8 W
Maximum: Approx. 3.6 W
0 ˚C - 40 ˚C (32 ˚F – 104 ˚F)
20 % – 80 % relative air humidity
(dry)
Approx. 178 mm × 115 mm × 101 mm
Approx. 340 g
Rechargeable Ni-MH battery
AAA (R03) size (1.2 V 400 mAh)
Super Heterodyne
PLL synthesizer
Quadrature Discriminator
13.824 MHz ±100 Hz
Frequency Modulation
40 bit
Tone (DTMF)/Pulse
Up to 48 digits
Up to 24 digits (Phonebook)
8 days at Standby,
10 hours at Talk
0 ˚C - 40 ˚C (32 ˚F – 104 ˚F)
20 % – 80 % relative air humidity
(dry)
Approx. 168
mm × 48 mm × 31 mm
Approx. 130 g
Base Unit Handset Charger
AC Adaptor
(PNLV226Z, 120 V AC, 60 Hz)
Standby: Approx. 0.1 W,
Maximum: Approx. 1.8 W
0 ˚C - 40 ˚C (32 ˚F – 104 ˚F)
20 % – 80 % relative air humidity
(dry)
Approx. 72 mm × 73 mm × 39 mm
Approx. 100 g
Duplex procedure:
TDMA (Time Division Multiple Access)
Channel spacing:
1,728 kHz
Bit rate:
1,152 kbit/s
Modulation:
GFSK (Gaussian Frequency Shift Keying)
RF transmission power:
115 mW (max.)
Voice coding:
ADPCM 32 kbit/s
■
■
■
■
■
■
■Standard:
DECT 6.0 (Digital Enhanced Cordless
Telecommunications 6.0)
■Number of channels:
60 Duplex Channels
■Frequency range:
1.92 GHz to 1.93 GHz

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KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
4 Technical Descriptions
4.1. US-DECT Description
The frequency range of 1.92 GHz-1.93 GHz is used. Transmitting and receiving carrier between base unit and handset is same
frequency. Refer to Frequency Table (P.61).
4.1.1. TDD Frame Format
4.1.2. TDMA system
This system is the cycles of 10 ms, and has 6 duplex paths, but maximum duplex communication path is 5 because of dummy
bearer use.
In 1 slot 417 μs, the 10 ms of voice data is transmitted.
•2 - Handsets Link
Traffic Bearer
A link is established between base unit and handset.
The state where duplex communication is performed.
Handset doesn't make up duplex in no free RF channels because of interference. (*1)
Dummy Bearer
Base unit sends Dummy-data to the all stand-by state handsets.
Handsets receive that data for synchronization and monitoring request from the base unit.
Base unit doesn't send Dummy bearer in no free RF channels because of interference. (*1)
Note:
(*1) It is a feature under FCC 15 regulation and for interference avoidance.
In the case of checking RF parts, it is better in least interference condition.
417 μs (available) 417 μs (blind)
5 ms 5 ms
Up Link ( Handset ->Base Unit ) Down Link ( Base Unit ->Handset )
DATA rate : 1.152 Mbps
RX1 RX2 RX3 RX4 RX5 RX6 TX1 TX2 TX3 TX4 TX5 TX6
RX1 RX2 RX3 RX4 RX5 RX6 TX1 TX2 TX3 TX4 TX5 TX6
TX RX
RXTX
Traffic Bearer Dummy bearer
Base unit
Handset 1
(Stand by)
Handset 2
(Link)
Handset 3
(Link)

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KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
4.1.3. Signal Flowchart in the Radio Parts
Reception
Base unit:
A voice signal from TEL line is encoded to digital data and converted into a 1.9GHz modulated radio signal by BBIC(IC501).
The RF signal, after which is amplified in BBIC, is fed to selected antenna.
Handset:
As for a handset RF, RF signal is received in one antenna.
BBIC down-converts to 864 kHz IF signal from RX signal and demodulates it to digital data "RXDATA".
BBIC (IC1) converts RXDATA into a voice signal and outputs it to speaker.
Transmission
Handset:
A voice signal from microphone is encoded to digital data and converted into a 1.9GHz modulated radio signal by BBIC(IC1).
The RF signal, after which is amplified in BBIC, is fed to an antenna.
Base unit:
As for a base unit RF, RF signal is received in two antennas.
BBIC (IC501) compares RF signal levels and selects the antenna to be used. Then BBIC down-converts to 864 kHz IF signal
from RX signal in the selected antenna, and demodulates it to digital data "RXDATA".
BBIC (IC501) converts RXDATA into a voice signal and outputs it to TEL line.

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KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
4.2. Block Diagram (Base Unit_Main)
Operational P.C. Board
D101
CHARGE_CONTACT
+
-
SP
X501
13.824 MHz
MIC
+-
ANT2ANT1
TEL JACK
L1T L1R DCP DCM
DC JACK
RLY
SIDE TONE CIRCUIT
Q161
Q141
BELL DETECT
HOOK
BELL
Q111
LIN
LOUT
RF_PART
HSMIP
HSMIN
IC501
BBIC
INUSE DETECT 2
INUSE DETECT 1
RECEIVE AMP
DCIN 1 DCIN 2
IC302
VCCPA
VBAT_APU
VBAT
VCC_FE
VCC_IF
VCC_VCO
DCINS
CHARGE_DET
3.0V
DOUBOUT
SCL, SDA
WP
VDD
ANS_LED
SP_LED
IC601
FLASH MEMORY
IC611
EEPROM MEMORY
KEYS LCD R151,R152 R131, R133
Q171
VBAT
DL,CS
MSG_LED
LCD_BLT
KEY 1
MIP
MIN
6
KEY A~E
CS, CD, SID
SCL, RST
SPOUTN
SPOUTP
3.0 V REGULATOR
Power supply at AC failure
CLK,DO
STM/CKM
R371 R372
Q701, Q702
CHARGE DETECT
VCCA
VCC
KX-TG6841/6842/6843/6844/6845/6873 BLOCK DIAGRAM (Base Unit_Main)
ANT2 ANT1 RXp RXn TXp TXn
RESET
RSTN

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KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
4.3. Block Diagram (Base Unit_RF Part)
KX-TG6841/6842/6843/6844/6845/6873 BLOCK DIAGRAM (Base Unit_RF Part)
DA802
ANT2
ANT1
RXp
RXn
ANT2
ANT1
TXp
TXn

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KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
4.4. Circuit Operation (Base Unit)
General Description:
(BBIC, Flash Memory, EERROM) is a digital speech/signal processing system that implements all the functions of speech
compression, record and playback, and memory management required in a digital telephone answering machine.
The BBIC system is fully controlled by a host processor. The host processor provides activation and control of all that functions
as follows.
4.4.1. BBIC (Base Band IC: IC501)
•Voice Message Recording/Play back
The BBIC system uses a proprietary speech compression technique to record and store voice message in Flash Memory.
An error correction algorithm is used to enable playback of these messages from the Flash Memory.
•DTMF Generator
When the DTMF data from the handset is received, the DTMF signal is output.
•Synthesized Voice (Pre-recorded message)
The BBIC implements synthesized Voice, utilizing the built in speech detector and a Flash Memory, which stored the vocabulary.
•Caller ID demodulation
The BBIC implements monitor and demodulate the FSK/DTMF signals that provide CID information from the Central Office.
•Digital Switching
The voice signal from telephone line is transmitted to the handset or the voice signal from the handset is transmitted to the
Telephone line, etc. They are determined by the signal path route operation of voice signal.
•Block Interface Circuit
RF part, LED, Key scan, Speaker, Telephone line.
4.4.2. Flash Memory (IC601)
Following information data is stored.
•Voice signal
ex: Pre-recorded Greeting message, Incoming message
4.4.3. EEPROM (IC611)
Following information data is stored.
•Settings
ex: message numbers, ID code, Flash Time, Tone/Pulse
RF part
ADPCM
Analog
Front
End
&
Multi-
plexer
TEL
Line
Interface
Digital
Speech
Processor
Caller ID
Modem
Digital TAM System
Flash Memory IC601
Host CPU
MIC
SP
BBIC (IC501)
DECT RF system
TDMA/TDD
Mod/Demod
PA/LNA ADPCM
Keys/ LEDs/ ChargeEEPROM IC611

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KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
4.4.4. Power Supply Circuit/Reset Circuit
The power supply voltage from AC adaptor is converted to VBAT (3.0V) in IC302. And +3.0V for peripherals and analog part is
insulated from VBAT by Doubler of BBIC.
Circuit Operation:
5.5V
VBAT
RSTN(Reset)
pin 54
VBAT
pin 10
pin 57
pin 9
pin 15
IC501
IC302 IC601
BBIC
DOUBLER OUT
For peripherals
VDDC (1.2V)
AC Adaptor 3.0V
REGULATOR
FLASH
IC611
EEPROM
+3.0V
STM/CKM
Receive
Amp.
RF Part
Q661 LCD BLT
ANS LED
MSG LED
SP LED
Startmonitor
(IC501 57pin)
VDDC (1.2 V)
VBAT
Reset (RSTN)
(IC501_54 pin)
BBIC chip initialize
(CKM/STM)
LCD_BLT (IC501-pin 33)
LCD

14
KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
4.4.4.1. Charge Circuit
The voltage from the AC adaptor is supplied to the charge circuits.
D362 R372 R371
D361
CHARGE+
F301 DCP
CHARGE-
( )
+5.5V
DCM

15
KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
4.4.5. Telephone Line Interface
Telephone Line Interface Circuit:
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, 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 →C111 →Q111 →BBIC pin 59
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
ON HOOK Circuit:
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.
Pulse Dial Circuit:
Pin 6 of BBIC turns Q141 ON/OFF to make the pulse dialing.
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 Q161 is
canceled by the canceller circuit of BBIC.
RX
Pin 16 of IC501
R176
R175
C178
C175
Q171
R172
R171
Hook
Pin 6 of IC501
Pin 28 of IC501
Pin 59 of IC501
TX
BELL
R177
C173
R165
R168
C167
R163
C142 D142
C168
R162
R145
R164
Q161
C163
R161 Q142
Q141
R142
R141
C184
C101
C102
D101
P101
SA101
SA102
L1R
TEL JACK
+3.0V
R114
R111C111C113
D113
C112 R112
R113
Q111
1
B
B
B
E
E
E
C
C
C
4
2
3
C176
L1T
C171
C161
C164
R160
12
AK
+3.0V

16
KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
4.4.6. Parallel Connection Detect Circuit/Auto Disconnect Circuit
Function:
In order to disable call waiting and stutter tone functions when using telephones connected in parallel, it is necessary to have a
circuit that judges whether a telephone connected in parallel is in use or not. This circuit determines whether the telephone
connected in parallel is on hook or off hook by detecting changes in the T/R voltage.
Circuit Operation:
Parallel connection detection when on hook:
When on hook, the voltage is monitored at pin 17 of IC501. There is no parallel connection if the voltage is
0.54 V or higher, while a parallel connection is deemed to exist if the voltage is lower.
Parallel connection detection when off hook:
When off hook, the voltage is monitored at pin 18 of IC501; the presence/absence of a parallel connection is determined by
detecting the voltage changes.
If the Auto disconnect function is ON and statuses are Hold, receiving ICM, OGM transmitting, BBIC disconnects the line after
detecting parallel connection is off hook.
Pin 18 of IC501
Pin 17 of IC501
Pin 6 of IC501
HOOK
B
E C
BC
E
B
C
E
21
1
43
2
R131
L1R
C152
R161
R133
R141
R151
L1T
C132
Q141
R142
R145
P101
RA151
RA151
Q142
Q161
R162
SA101
SA102
C168
C163
D101
C101
C102
R163
R152
DCIN2
DCIN1

17
KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
4.4.7. Calling Line Identification (Caller ID)/Call Waiting Caller ID
Function:
Caller ID
The caller ID is a chargeable ID which the user of a telephone circuit obtains by entering a contract with the telephone company
to utilize a caller ID service. For this reason, the operation of this circuit assumes that a caller ID service contract has been
entered for the circuit being used. The data for the caller ID from the telephone exchange is sent during the interval between the
first and second rings of the bell signal. The data from the telephone exchange is a modem signal which is modulated in an FSK
(Frequency Shift Keying) * format. Data "1"is a 1200 Hz sine wave, and data "0"is a 2200 Hz sine wave. There are two types of
the message format which can be received: i.e. the single message format and plural message format. The plural message
format allows to transmit the name and data code information in addition to the time and telephone number data.
*: Also the telephone exchange service provides other formats.
1st Ring
2 sec Silent interval 4 sec
2nd Ring
2 sec
0.5 s 575 ms min 0.5 s
DATA
0.1 Vrms
STD Ring / 20 Hz
Tip-Ring
DATA in
A
BDATA out
1200 Hz
=DATA "1"
1 bit=833 µs
2200 Hz
=DATA "0 "
70 Vrms
month day hour minute number
201348700035161504
Single message format
Plural message format
1st Ring
2 sec
718 ms 2nd Ring
0.5 s
DATA
month day hour minute number
20134870003516 16
DATA CODE NAME
201 John Smith 04

18
KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
Call Waiting Caller ID
Calling Identity Delivery on Call Waiting (CIDCW) is a CLASS service that allows a customer, while off-hook on an existing call,
to receive information about a calling party on a waited call. The transmission of the calling information takes place almost
immediately after the customer is alerted to the new call so he/she can use this information to decide whether to take the new
call.
Function:
The telephone exchange transmits or receives CAS and ACK signals through each voice RX/TX route. Then FSK data and
MARK data pass the following route.
Telephone Line →P101 →C121, C122 →R121, R122 →IC501 (25, 24).
If the unit deems that a telephone connected in parallel is in use, ACK is not returned even if CAS is received, and the
information for the second and subsequent callers is not displayed on the portable handset display.
CAS
CAS: CPE Alerting Signal
Dual Tone of 2130 Hz, 2750 Hz
-15 dBm (900 ohm load)
80 5 ms
MARK DATA
0~500 ms 58~75 ms about 300 ms
(be changed by
Information Volume)
Continuance Signal
of 1200 Hz (Data "1") "FSK"
ACK: Acknowledged Signal
DTMF
"D"
ACK
0~100 ms 60 5 ms
Telephone Exchange Cordless phone
Cordless phone
Signal Flow
Signal Flow
Telephone Exchange
Call Waiting Format
C121
R121
C122
P101
L1T
L1R
SA101
R122
C120
25
24
BBIC
IC501
"FSK"
data
Telephone
Line

19
KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
4.5. Block Diagram (Handset)
IC1
IC3
MIP
MIN
HSSPOUTP
LOUT
HSMIP
HEADSET_DET
SPOUTP
SPOUTN
CKM//STM
CKM/STM
BBIC
RESET
CHG_CTL
BATTERY_ON
CHG_DET
WP, CLK, DATA
KEYSTOROBE_A~E
KEYIN_1~5
CHARGE
MIC
Receiver
Headset Jack
CN431
Monitor SP
LCD
CHARGE
PUMP
IC4
KEYS
RF part
ANT1
X1
13.824 MHz
EEPROM
3V
BATTERY
LED
(LCD)
RSTN
VBAT
VBAT
3V
4.0V VBAT
RXn
RXp
TXp
TXn
KX-TGA680 BLOCK DIAGRAM (Handset)
KEY_LED
CP_OFF
Q6
LED
(KEY)
4V
CHARGE
CONTROL
POWER SUPPLY
CONTROL

20
KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
4.6. Block Diagram (Handset_RF Part)
KX-TGA680 BLOCK DIAGRAM (Handset_RF Part)
RXp
RXn
ANT
TXp
TXn