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9

2. Handset call 

Transmitting signal is input from handset microphone and amplified by IC103 

→ input to IC501-pin J1 → A/D conversion, Gain

adjustment by a built-in DSP of IC501.
Receiving signal input from IP Line 

→ Gain adjustment and D/A conversion by DSP of IC501 → output from IC501-pin H1,G1

→ output to handset speaker.

3. Headset Call

Transmitting signal is input from headset microphone and amplified by IC105 

→ input to IC501-pin H4 → A/D conversion,

Gain adjustment by a built-in DSP of IC501.
Receiving signal input from IP Line 

→ Gain adjustment and D/A conversion by DSP of IC501 → output from IC501-pin E2 →

output to headset speaker.

+

-

AG3

HSMICINP

C115

OPBIAS

MICBIAS

AG

AG3

AG

AG

JK101

1
2
3
4

5

R132

R133

IC103

5

6

7

C127

C128

R122

R123

C109

C124

R128

R129

D103

D104

D105

C125

C137

C139

C179

C180

C181

DG

DG

DG

DG

R112

R153

C186

AG3

C107

DG

DG

C143

C141

L108

L107

DG

DG

C189

C188

C146

C147

R120

R121

D106

L106

L105

IC501

BBIC

C542

DG

J1

H1

G1

+

-

AG2

R144

MICBIAS2

AG2

C164

AG2

OPBIAS2

AG2

R143

HESMIC2

HESSPOUT2

IC105

3

2

1

C168

R142

C161

C165

C169

C167

C166

C170

L112

C178

AG2

R137

R155

C160

CN101 CN205

2

3

C187

AG2

R140

R141

IC501

BBIC

R547

H4

E2

C221

C217

C218

JK202

1

4

2

3

5

C226

C205

D245

21

D247

21

D246

21

L210

L209

L208

10

11

AG

AG

C207

R223

HEADGND

ASIC

IC205

HEADGND

HEADGND

HEADGND

HEADGND

L212

AG

HEADGND

10

IC205 controls KEY, LED, EHS and Headset-detect.
An operating clock is provided by IC501 and a reset signal from the IC501 starts either reset or normal operating.(L(0V):RESET)
The IC205 and IC501 are connected by an I2C communication.
IC501 checks the presence of IC205 by getting the signal from IC205.

LED and KEY Timing chart
The LED control and the KEY control use the same strobe(STB) signal. 
Therefore, the LED control and the KEY control are alternately executed. 
The timing chart is as shown in the following .

11

The key data is under the matrix control by IC205.
The key information output from LED_STB is input into KEYIN, when the key is pressed.

The HOOK key is independent from Key Scan Matrix and taken into the port singularly.

KEY Input control timing chart
KEYIN pins have a internal pull-down resistor.
If KEY is pushed, high level is latched by connecting STB(output high) and KEYIN. If not, low level is latched.
The value is fixed by reading twice. 

12

The lighting of the LEDs is controlled by IC205.
Ringer LEDs are static lighting system.
Other LEDs light up in a dynamic lighting system.
The duty ratio is 1/10 (ON time 1.6ms).