Rockwell Automation 1770 DH,DHII,DH485 CABLE - Manual (Page 46)

Chapter 3
Constructing a Data Highway or
Data Highway Plus Cable System
3-14
Attach these wires: To this terminal number:
Two blue conductor wires (one
from each trunkline segment)
1
Two drain wires (one from each
trunkline segment)
2
Two clear conductor wires (one
from each trunkline segment)
3
6. Secure the trunkline segments by tightening the cable clamps around them.
After all of the droplines and trunkline segments have been connected together,
you must install a 150-ohm terminating resistor at each end of the trunkline.
Refer to the next section for instructions.
Terminate the Trunkline
To minimize signal reflections from the ends of the trunkline, you must attach a
150-ohm 1/2 watt terminating resistor on the first and last station connectors on
the trunkline. (The terms ‘‘first” and ‘‘last” refer to the physical location of the
node along the trunkline, and not the node’s station number.)
To install the terminating resistors, refer to Figure 3.3 and follow these steps.
1. Connect the dropline to the station connector. Refer to the procedure
explained earlier in this chapter for instructions.
2. Connect the one trunkline segment to the station connector. Refer to the
procedure explained earlier in this chapter for instructions.
3. Slip a one-inch (2.5 cm) length of shrink tubing over the 150-ohm
terminating resistor and connect the leads of the resistor to screw-clamp
terminals 1 and 3.
4. Insert the cable clamp plug into the unused cable clamp on the station
connector. Tighten the cable clamp to hold the plug securely in place.
Repeat steps 1 through 4 at the other end of the trunkline.
After all the necessary connections are made to the station connector, you must
mount the station connector to a secure foundation. Refer to the next section for
instructions.