Rockwell Automation 1770 DH,DHII,DH485 CABLE - Manual (Page 62)

Chapter 3
Constructing a Data Highway or
Data Highway Plus Cable System
3-30
Figure 3.7 shows a more detailed view of the attachments to the T-connector.
Figure 3.7
Attachments to the TĆconnector.
Jack
Leg
Jack
Leg
Plug Connector
Plug Connector
Plug Leg
Jack Connector
Trunkline Segment
11618
1. Attach the jack connector of one trunkline segment to the plug leg of the
T-connector.
2. Attach the plug connector of the other trunkline segment to one of the jack
legs of the T-connector.
3. Attach the plug connector of the dropline to the other jack leg of the
T-connector.
4. Repeat steps 1 through 3 for other droplines and trunkline segments.
After all of the droplines and trunkline segments have been connected together,
you must install a terminator at each end of the trunkline. Refer to the next
procedure for instructions.
Terminate the Trunkline
The T-connectors on the ends of the trunkline have a dropline and only one
trunkline segment connected to each of them. This leaves two open, or
unterminated, ends on the trunkline. Signals transmitted along the DH cable
could reflect off these unterminated ends and interfere with transmissions.
To minimize signal reflections from the ends of the trunkline, you must attach
terminators (Figure 3.8) to the first and last T-connectors on the trunkline. (The
terms ‘‘first” and ‘‘last” refer to the physical location along the trunkline.)