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1. Function

This unit has a lithium battery (BAT300) which works for the Real Time Clock IC (RTC: inside IC300).
The RTC continues to work, backed up by a lithium battery even when the power switch is OFF.

2. RTC Inside (IC300) Backup Circuit Operation

When the power switch is turned ON, power is supplied to the RTC (inside IC300). At this time, the voltage at pin AD4 of the
IC300 is +3.3V. When the power switch is turned OFF, the BAT300 supplies power to RTC through DA300. 
When the power switch is OFF and the voltage of +3.3V decreases, pin AD4 of RTC (IC300) becomes roughly the same volt-
age as the battery voltage. RTC goes into the backup mode, in which the power consumption is lower.

The modem (Included IC300) has all the hardware satisfying the CCITT standards mentioned previously.
ALL processing is controlled by the SOC (IC300) according to CCITT procedures.
This modem (Included IC300) has an automatic application equalizer. With training signal 1 or 2 at the time of G3 reception, it can
automatically establish the optimum equalizer.

The digital image data sent on ATXD line from modem (Included IC300).
DAA IC100(6

→9,10), Line side DAA IC101 and the NCU section to the telephone line.

The analog image data which is received from the telephone line passes through the NCU section and enters line side DAA*

IC100. The signals are changed to digital data in IC100 (5,6), IC101(9,10

→5) and IC300. In this case, the image signals from

the telephone line are transmitted serially. Here, the internal equalizer circuit reduces the image signals to a long-distance
receiving level. This is designed to correct the characteristics of the frequency band centered around 3 kHz and maintain a con-
stant receiving sensitivity.

W02

SDMD7

I/O

3.3V

SDRAM DATA BUS 7

W03

SDMA11

O

3.3V

SDRAM ADDRESS BUS 11

W04

SDMA9

O

3.3V

SDRAM ADDRESS BUS 9

W23

PSCIO16

O

3.3V

NOT USED

W24

PSCIO17

O

3.3V

NOT USED

W25

PSCIO18

I

3.3V

INPUT PORT (TOPCVR)

W26

PSCIO19

I

3.3V

INPUT PORT (REGIST)

Y01

VSS

-

GND

GND

Y02

SDCLK

O

3.3V

SDRAM CLOCK 1

Y03

SDMA8

O

3.3V

SDRAM ADDRESS BUS 8

Y04

VSS

-

GND

GND

Y23

AFESEL0

I

3.3V

NCU INTERFACE

Y24

AFESEL1

I

3.3V

NCU INTERFACE

Y25

EXMDMCS

O

3.3V

NOT USED

Y26

DP

O

3.3V

NCU INTERFACE

PIN NO.

PinName

I/O

POWER SUPPLY VOLTAGE

EXPLANATION

26

The path is the same as Facsimile Reception.

This is the call signal which is generated the SOC (IC300) and sent to the speaker.

 DAA : Direct Access Arrangement

Composed of ITS circuit and NCU circuit.

The analog section works as an interface between the telephone line.
DAA control ITS circuit and NCU circuit. 
DAA control signals are output from Soc IC300.

[NCU]: Network Control Unit the NCU comprises of the following; DC loop forming circuit to connect with the telephone line;
Switching circuit for other interconnected telephones; Bell detection circuit; Remote fax activation circuit.
Refer to NCU SECTION (P.27) for the details.

RING

ARXD

ATXD

BTXD

BRXD

IC200

IC100

IC101

EXTRLY

T

R

T

R

SP(+)

SP(-)

HS_MIC(+)

HS_MIC(+)

HS_SP(+)
HS_SP(-)

AGC

15

5

6

5

6

10

9

8

9

15

1

16

14

12

1

3

13

4

5

10

16

KX-FLB662CX/KX-FLB672CX: MAIN BOARD BLOCK DIAGRAM

27

This section is the interface between the telephone line and external telephone. It is composed of an EXT. TEL line relay (RLY100),
bell detection circuit, TAM interface circuit and line amplifier.

1. Circuit Operation

Normally, this relay switches to the external telephone side and switches to the open side while OFF-HOOK.
IC300 (U25) High Level

→Q100 ON→RY100 (ON)

1. Circuit Operation

The signal waveform is indicated below. The bell signal input to IC101 and ring detected signal output from pin 15 of IC100.
IC300 monitor this signal and judged as bell.
TEL LINE

→IC101 (8,9 - 5,6)→IC100 (9,10 - 15)→IC300(L23)

1. Function

This unit is compatible with the Caller ID service offered by your local telephone company. To use this feature, you must sub-
scribe to a Caller ID service. 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 “0” is a 1200 Hz sine wave, and data 1 a 2200 Hz sine wave.
There are two type of the message format which can be received: i.e.the single data message format and multiple data mes-
sage format.
The multiple data format allows to transmit the name and data code information in addition to the time and telephone number
data.
When there is multiple data in the unit, the name or telephone number are displayed.

2. Circuit Operation

The caller ID signal input from TEL LINE is processed with Soc (IC300).
TEL LINE

→IC101 (8,9 - 5,6)→IC100 (9,10 - 5)→IC300(AD26)

1. Function

Another telephone connected to same line activates the unit to the FAX mode by using a DTMF signal.

2. Signal Path

TEL LINE

→IC101 (8,9 - 5,6)→IC100 (9,10 - 5)→IC300(AD26)

This circuit is to switch between FAX receiving and the external TAM’s message recording automatically. 
For details, please refer to TAM INTERFACE SECTION (P.28).

28

The general ITS operation is performed by IC200 which has a handset circuit. The alarm tone, the key tone, and the beep are
output from Soc IC300.

1. Function

This is the function when you are not holding the handset and can hear the caller’s voice from the line.

2. Circuit Operation

(Telephone Monitor Signal Path)
Signals received from the telephone line are output through at the speaker via the following path.

3. Signal Path

TEL LINE

→D103→Q104→C106→IC101(3-5,6)→IC100(9,10-5)→IC300(AD26-AB24)→IC200(4-1)→IC202(2-1)→IC204(4-

5,8)

→CN200(7,8)→CN5(7,8)→CN6(1,2)→SPEAKER

1. Function

This circuit monitors various tones, such as (1) DTMF tone, (2) Alarm/Beep/Key tone/Bell.

2. Signal Path

a. DTMF MONITOR

(Speaker Operation)
IC300(AB24)

→IC200(4-1)→IC202(2-1)→IC204(4-5,8)→CN200(7,8)→CN5(7,8)→CN6(1,2)→SPEAKER

(Handset Operation)
IC300(AB24)

→IC200(4-16)→IC203(4-8)→CN200(5,6)→CN5(5,6)→CN7(2,3)→HANDSET UNIT

b. ALARM/BEEP/KEY TONE/BELL

IC300(B20)

→IC202(2-1)→IC204(4-5,8)→CN200(7,8)→CN5(7,8)→CN6(1,2)→SPEAKER

1. Function

When TAM is connected to this unit, the unit receives documents for FAX calls or the external TAM records a voice message
automatically.

2. Circuit Operation

The TAM INTERFACE circuit consists of Soc(IC300) to detect the other party CNG signal, and RLY100 to separate EXT.TAM.

a. CNG signal detection circuit

The CNG signal from the other party’s FAX is detected in Soc IC300 
(Signal path)
TEL LINE

→IC101 (8,9 - 5,6)→IC100 (9,10 - 5)→IC300(AD26)

b. Remote receiving

This is the parallel-connected DTMF signal for the TEL or EXT.TEL mode between T and R. When the other party is a
FAX, the unit switches to FAX receiving.
(Signal Path)
TEL LINE

→IC101 (8,9 - 5,6)→IC100 (9,10 - 5)→IC300(AD26)