Toshiba GD-1221, GD-1220 service manual CI detection circuit, Line 1 CI Detect Signal IC23

Models: GD-1220 GD-1221

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4.2.5CI detection circuit

NA/TW models

NCU board

+12V RLY2 CML relay

FAX board

MAIN board

112

Q51

3

3 CML1 27

27 144

4

Lb

9

1

 

0

10

 

 

 

 

Line

CN10

 

1

 

 

 

 

 

 

 

3 La 4

0

3

 

 

 

 

ZD1 ZD3 C1 R2

D52

AG 5VPS

R79

17

14

PC2

23

SG

CN9

CN262

17 CI1 65

CN5

CN5

65 162

IC23

ASIC

Fig. 4-10

The CI detection circuit consists of the photocoupler (PC2), ASIC (IC23) on the MAIN board and the other peripheral devices to detect a ring signal input from the telephone line.

The ASIC makes the CML1 signal become LOW to connect the CI detection circuit to the telephone line.

When a ring signal is input from the telephone line, the photocoupler is repeatedly turned ON/OFF. This allows the CI1 signal to become a pulse signal and input to the ASIC on the MAIN board, thereby detecting the ring signal.

Signal Name

Type

Active

Description

Destination

 

 

 

 

 

CI1

I

-

Line 1 CI Detect Signal

IC23

 

 

 

 

 

GD-1220/1221

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Page 70
Image 70
Toshiba GD-1221, GD-1220 service manual CI detection circuit, Line 1 CI Detect Signal IC23