Installation Guide
MX1
Fire Alarm System (NZ)
LT0360 ISSUE 2.43
29 NOVEMBER 2017
PAGE 16
SHLD
RXA+
RXA
-
TXA+
TXA-
RS485 PORT 1
SHLD
TXB-
TXB+
RXB-
RXB+
RS485 PORT 2
LK 11
LK 13
LK12
LK14
S
H
L
D
R
X
A
+
R
X
A
-
T
X
A
+
T
X
A
-
R
S
4
8
5
P
O
R
T
1
S
H
L
D
T
X
B
-
T
X
B
+
R
X
B
-
R
X
B
+
R
S
4
8
5
P
O
R
T
2
L
K
1
1
L
K
1
3
L
K
1
2
L
K
1
4
S
H
L
D
R
X
A
+
R
X
A
-
T
X
A
+
T
X
A
-
R
S
4
8
5
P
O
R
T
1
S
H
L
D
T
X
B
-
T
X
B
+
R
X
B
-
R
X
B
+
R
S
4
8
5
P
O
R
T
2
L
K
1
1
L
K
1
3
L
K
1
2
L
K
1
4
TXB-
TXB+
RXA-
RXA+
RXA+
RXA-
TXB+
TXB-
TX
B
-
TX
B
+
R
X
A
-
R
X
A
+
Figure 23
– I-HUB Ring Wiring
Links LK11, LK12, LK13 and LK14 must be installed on each I-HUB.
Wire the RS485 ring, preferably using shielded cable, from Port 2 TXB+ and TXB- to Port 1 RXA+ and RXA- on the
next I-HUB, repeating around the ring. The cable shields should be wired to the shield terminals. The two shield
screw terminals are joined together and are isolated from the chassis and I-HUB power grounds.
In ring mode, the I-HUB network ports 1 and 2 are pre-configured to operate at 57,600 baud. The recommended
maximum cable length is 300 meters un-terminated (when using 0.75mm² screened cable). When ports 1 and 2 are
terminated, the cable length (0.75mm² screened cable) may be increased to 1,500 meters. Termination is detailed
in Section 3.9 of the I-HUB User Manual (LT0229).
I-HUB Fibre Optic Ring
Ports 1 and 2 can be combined to operate in a 2-wire ring arrangement with other I-HUBs using fibre optic modems
and fibre optic cable. Fibre optic modems convert the RS485 signal interface into optical signals for transfer via
optical cable. Fibre optic transmission is not affected by ele
ctrically ‘noisy’ environments and offers significant
advantage where long ‘cable’ lengths are required.
For fibre segments, I-HUB links LK11 and LK13 (Port 1), LK12 and LK14 (Port 2), (located either side of the screw
terminal block) must be removed.
Figure 24 shows a wiring diagram for use with OSD139AF optical modems. These are the recommended fibre optic
modems for use with the I-HUB. These units support a maximum baud rate of 57,600 over two fibres per leg. The
DTE/DCE switch needs to be set in the DTE position.
SHLD
RXA+
RXA-
TXA+
TXA-
RS485 PORT 1
SHLD
TXB-
TXB+
RXB-
RXB+
RS485 PORT 2
LK11
LK13
LK12
LK14
SHLD
RXA+
RXA-
TXA+
TXA-
RS485 PORT 1
SHLD
TXB-
TXB+
RXB-
RXB+
RS485 PORT 2
LK11
LK13
LK12
LK14
OSD139
RX
TX
TO NEXT I-HUB
FROM PREV I-HUB
+24VDC
+24VDC
OSD139
RX
TX
I-HUB PTS0006
LM0572
LM0572
0V
0V
Figure 24
– I-HUB Fibre Ring Wiring
