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The general ITS operation is performed by the modem IC5. The alarm tone, the key tone, the calling tone and the beep are output
from the ASIC IC1 (digital board). 

1. Function

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

2. Signal path

Refer to Check Sheet for Signal Route (P.114)

1. Function

The circuit controls the automatic switching of the transmitted and received signals, to and from the telephone line, when the
unit is used in the hands-free mode.

2. Circuit Operation

The speakerphone can only provide duplex.

3. Signal path

Refer to Check Sheet for Signal Route (P.114)

1. Function

This circuit controls the conversation over the handset, i.e. the transmitted and received voices to and from the handset.

2. Signal path

Refer to Check Sheet for Signal Route (P.114)

1. Function

This circuit monitors various tones, such as 1 DTMF tone, 2 Alarm/Beep/Key tone/Bell  3 Dummy ring back tone.

2. Signal path

Refer to Check Sheet for Signal Route (P.114)

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 a CNG signal from the other party’s detection circuit, VOX detection circuit (to judge
sound/no-sound) and RLY101 (to separate EXT. TAM).

a. CNG/VOX signal detection circuit

The CNG signal from the other party’s FAX is detected in MODEM IC5 (digital board).

b. Remote receiving

This is the parallel connected DTMF signal for the TEL mode between a and b. When the other party is a FAX, the unit
changes to FAX receiving.

3. Signal path

Refer to Check Sheet for Signal Route (P.114)

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1. Function

The ATAS main operation is performed by the special IC5 (MODEM). IC6 (FLASH MEMORY) control signals are input from
ASIC IC1.

a. Greeting/Message Recording
b. ICM Recording

c. Greeting/Message/ICM play to speaker

d. Greeting/Message/ICM play to Tel Line
e. Vox Detection

2. Signal Path

Refer to Check Sheet for Signal Route (P.114)

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The unit consists of a LCD (Liquid crystal display), KEYs and LEDs (light-emitting diodes). They are controlled by the Gate Array
(IC301) and ASIC (IC1: on the DIGITAL BOARD). The key matrix table is shown below.

CN301

CN7

IC1

ASIC

(Chip on board type)

LCD

GATE ARRAY

IC301

CN302

DOCUMENT TOP SENSOR
DOCUMENT SET SENSOR

8 x 5

KEYS

MATRIX

LED

D301

DIGITAL BOARD

OPERATION BOARD

KX-FT982 / KX-FT984 / KX-FT988: OPERATION BOARD: BLOCK DIAGRAM

XLED8, 9

KIN0~7

XLED13

KSL0~4

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The Gate Array IC(IC301) works only for writing the ASCII code from the data bus (D4~D7). V0 is supplied for the crystal drive. 
R312, R313, R314 and R316 are density control resistors. 
Consequently, in this unit, the timing (positive clock) is generated by the LCD interface circuitry in the gate array (IC301).

DIsplay mode

Density

Normal

Dark

English font
(Global)
2 lines

LED1 (IC301-22pin)

H

L

LED15 (IC301-21pin)

L

L

LED14 (IC301-20pin)

Hi-Z

L