![background image](http://html1.mh-extra.com/html/panasonic/kx-dt543-b/kx-dt543-b_service-manual_3785546009.webp)
9
KX-DT543/KX-DT543-B/KX-DT546/KX-DT546-B
4.2.4.
DXDP Communication
Function:
This circuit performs the same type of communication as between the DPT and PBX, but a slave DPT for DXDP is connected to
the DXDP port.
In addition, it controls power feeding for a slave DPT.
Circuit Operation:
The data to the slave DPT is output from pins 47 and 48 of IC300 and sent via “Q331
C331” and “Q332
C337” to JK301.
The data from the slave DPT is sent through “C337
R350” and is input to the comparator (pin 22) built in IC300.
The threshold voltage of the comparator is determined by R353, R354 and R355. It is input into pin 21 and 23 of IC300.
Power is controlled to the Slave DPT by means of a constant current circuit Q303 and Q304 as below:
• IC300 pin 20 H: Constant current circuit ON.
• IC300 pin 20 L: Constant current circuit OFF.
• IC300 pin 25 H: 40mA feed (normal supply to Slave DPT).
• IC300 pin 25 L: 20mA feed (initial supply to Slave DPT).
J
K301
1
2
3
4
5
Q
303
Q
304
1
E1
2
B1
3
C
2
4
E
2
5
B
2
6
C1
H-D
L-D
R319
R3
2
0
C31
2
C313
C3
2
5
R3
22
DG
R3
2
1
PG
PG
PG
C33
2
C331
R34
2
R343
V
DD33
DG
DG
DG
C330
R340
R341
R31
2
R313
Q
33
2
1
E1
2
B1
3 C
2
4
E
2
5
B
2
6
C1
DG
C33
7
R348
R349
DG
V
DD33
DG
C333
DG
C334
V
DD3
V
DD33
C335
DG
C33
6
R350
R351
R35
2
R353
R354
R355
DG
DG
DG
D53
2
D533
L303
L304
Q
331
1 B1
2
E
3 B
2
5
C1
4
C
2
Q
330
R345
R34
6
R34
7
TO DPT/
S
LT
IC300
AS
IC1
4
7
48
DD
X
0
DD
X
1
D
V
RH
2
3
22
DDR
2
1
D
V
RL
2
0
GPIO3
2
5
GPIO4