6 
4.3  Setting the Communications Module Jumpers 
Prior to installing the Communications Module into the MJ-4 Control Panel, ensure that the jumpers are properly 
installed on the printed circuit board. Jumper selections for the Fiber Optic interface and RS232/485 interface are 
described in separate sections below. 
4.3.1  Fiber Optic Interface 
The jumper locations for the fiber optic interface are shown in Figure 4-3. The view of the module is from the 
component side. The fiber optic receiver (RX) and transmitter (TX) are shown for reference. The jumper settings 
are listed in Table 4-1. 
Set Auto Repeat to “No Repeat” when only one unit is installed in the network. 
J11
J10
J12
1
2
J14
1
2
3
 
Figure 4-3 Fiber Optic Interface Jumper Locations. 
Table 4-1 Fiber Optic Interface Jumper Settings 
Jumper  Name  Position  Function Selected  State Description 
1-2 
Auto Repeat  Repeat message from Host and any responses from
other IEDs     (Auto repeat for mark 0 or mark 1) 
2-3  No Repeat  Transmit continuously ON (for testing) (Force 0) 
J14 Auto Repeat 
Out  No Repeat  Only transmit a response if being addressed by Host 
(no jumper installed at 1-2 or 2-3) (Force 1) 
Out 
Normal  Set Low Power Transmitter Output 
J12 Range 
In   Long  Set High Power Transmitter Output (See Note 2) 
Note 1: Default pin settings are shown in bold text. 
Note 2: If 50/125 µm cable is used, J12 must be jumpered (In).  
4.3.2  RS-232/485 Interface 
Figure 4-4 shows the jumper locations for the RS-232/485 interface, viewed from the component side. Jumpers and 
their default settings are listed in Table 4-2.  
1
2
J11
1
2
3
J10
J12
J14
 
Figure 4-4 RS-232/485 Interface Jumper Locations.