KX-T7440CB, KX-T7440C - Panasonic PBX Service Manual (repair manual). Page 10

−

10

−

Start Signal

18

DIN

13

32

μ

s

6.4

μ

s

DCLR

12

COUT

32

μ

s 6.4

μ

s

(19 pulses)

(47 pulses)

Acknowledge signal

1) Function
The data communication circuit serves the following functions:
Information exchanger between DSHS and DSS console, key input information as well as data for the LED control, etc.
This information is continuously at times.

2) Circuit Operation
When the DSS console receives an IRQ signal from the DSHS and after sending the key input information (19 pulses) to the
DSHS and receiving data (47 pulses) for LED control, etc. The DSS console will return to the DSHS an acknowledge signal.

3) Reception
The data from the DSS console is received via the H and L line along the path shown below.
H, L Line 

→

 D1 

→

 T1 

→

 R49 

→

 Q43 

→

 IC2 

→

 IC3 

18

4)Transmission
The data to the DSS console is transmitted along the following path.
IC3 

12

  

→

 IC2 

→

 R45 

→

 Q44 

→

 T1 

→

 P1 

→

 H, L line.

12

19

18

13

V1(+5V)

1

1

1
2

3

13
12

11

9
8

10

5
6

4

10

9

4

5

7

6

1

2

4

4

1

H

L

1

3

2

3

2

G

O

I

3

O

I

G

2

V2(+5V)

IC1

D1

+ ~

~

–

JP2

L1

JP3

V1

R46

R45

V1

V1

C4

R47

Q44

Q43

T1

R51

R56

R49

R48

IC2

IC2

IC2

R44

R43

C3

R50

D73

C5

IC2

DOUT

DINT

IC3

DIN

DCLR

JK1

IC4

C8

C7

C6

C1

1

C10

C9