KX-HT82480, KX-HT82470, KX-HT82460 - Panasonic PBX Service Manual (repair manual). Page 12

12

Making DP[0-3] pin of DSP becomes Low level, and PC902A-D turns ON and the line is acquired.
It is used in common as Dial Pulse transmitting circuit.

1. Ring 

 D902  D906  D908  Q900(C-E)  Q904(C-E)  R920  D908  Tip

2. Tip 

 D908  R920  Q904(C-E)  Q900(C-E)  D908  D906  D902  Ring

After line acquisition, DC and/or AC characteristics (Dynamic Range and Distortion etc) are controlled by current controll function of
DC Loop Circuit.
Also it provides the SHUNT control function for the stabilization of line power depending on the destination. Turning on  PC903A-D
when transmitting pulse reduces the impedance at making, and stabilizes the line power.

DTMF signal is generated by DTMF generator in the DSP device.

+

-

+

-

+

-

REVDET[0]

DP[0]

*RL900A

NC

1

2

3

4

*D904A

2

1

R930A

C926A

IC909A

3

2

1

R944A

D910A

+3.3V_DE56_2

C930A

C935A

C901A

+3.3V_DE56_2

VH1

DG

+3.3V_DE56_2

+3.3V_DE56_2

IC909A

5

6

7

R943A

PC900A

1

23

4

VH1

C904A

C924A

DG

R936A

C921A

C933A

DG

PC903A

1

2

3

4

R920A

C908A

+3.3V_DE56_2

*R901A

+3.3V_DE56_2

R946A

Q900A

C906A

*C905A

*C907A

D908A

3

1

2

4

DG

PC902A

1

3

4

6

*C912A

T900A

3

1

6

4

5

*D902A

*D906A

R981A

VH1

R980A

DG

C960A

*ZNR900A

*R908A

*R932A

*C916A

*R938A

*C918A

*R954A

*C928A

*R906A

*R904A

*R948A

*R922A

*R916A

*R934A

*R940A

PC901A

1

2

3

4

*C910A

*Q904A

*R900A

R902A

R914A

R918A

R924A

R926A

R928A

R950A

R956A

+

-

+

-

SIGN6843

C926A

IC909A

3

2

1

R944A

C930A

C935A

VH1

DG

IC909A

5

6

7

R943A

VH1

C924A

IC909A

4

VEE

8

VCC

R936A

C921A

C933A

+15V

R946A

*C912A

T900A

3

1

6

4

5

R981A

VH1

R980A

DG

C960A

*C937A

*R932A

*C916A

*R938A

*C918A

*R954A

*C928A

*R948A

*R934A

*R940A

R950A

R956A

From DSP