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SD39RIO-1 INSTALLATION
January 2001
2-25
2.5.4 IOBUS Cable Connection up to 1500 ft. (460 m)
for Rack-to-Rack Redundant APACS+ and all QUADLOG Systems
This section describes the preparation and installation of IOBUS cables for rack-to-rack redundant APACS+
or non-redundant and rack-to-rack redundant QUADLOG systems when the needed cable length exceeds the
maximum standard length of 98.4 ft. (30 m) of factory-prepared IOBUS cables but is less than 1500 ft. (460
m). This procedure involves splicing of W2040 and Belden

8627 extension cables between a Remote I/O
Rack and another type of rack (e.g., MODULRAC or SIXRAC), or between two remotely located Remote
I/O Racks.
The cable preparation procedure provided here involves splicing a custom-length cables that have unprepared
ends. These kinds of cable are type W2040 and Belden 8627. They are intended for use as a IOBUS
extension cables.
The Remote I/O Rack can accommodate either prepared or unprepared ends of available IOBUS cable(s). A
prepared cable end has a molded connector on it and is to be plugged into the appropriate IOBUS IN or
IOBUS OUT connector on the rack’s backplane (see Figure 2-4). The wires emerging from an unprepared
cable end are to be individually stripped and connected directly to the screw terminals of the associated
IOBUS IN or IOBUS OUT terminal block, also located on the rack’s backplane (see Figure 2-4).
When another type of rack (e.g., MODULRAC or SIXRAC) is also used, it requires a prepared cable end
(with a connector) to attach that rack to the IOBUS. In these instances, you must supply DIN rail-mounted
style terminal blocks (one for A side and one for B side). The terminal blocks are needed to transition
between W2040 and Belden 8627 unprepared cable ends and another cable segments that has a prepared end
(usually obtained by cutting a standard IOBUS cable in half). Each terminal block must be able to
accommodate wire sizes of 16 to 28 AWG (1,3 mm
2
to 0.09 mm
2
).
IMPORTANT
It is important to preserve continuous cable impedance through all splice
connections. This is to minimize signal reflections within the cable and help assure
collision-free communications. After preparing cable ends, make sure each intended
pair is re-twisted at the same intervals all the way to the screw terminals of the
terminal blocks. Refer to Figures 2-18 and 2-19.
To connect W2040 and 8627 IOBUS cables between a terminal block and a Remote I/O Rack:
1. Determine the length of W2040 and 8627 cables needed to connect from the terminal block location to
the appropriate IOBUS connection points on the Remote I/O Rack’s backplane. Allow slack for cable
stripping, dressing, tagging, and strain relief at each end.
2. At the user-supplied terminal blocks, provide strain relief for the W2040 and 8627 cable ends. Connect
the W2040 and 8627 cable conductors (wires) to the terminal blocks as shown in Figure 2-18. Note that
W2040 cable conductors are twisted together and shielded, but this is not required for 8627 cable
conductors. Wire stripping and color code information for making connections are provided in Table 2-1
and Figures 2-14 and 2-17.