Rockwell Automation 57C570 AutoMax PC3000 User Manual - Manual (Page 47)

3Ć9
75ĆOhm Terminating Load
The DCSĆNET network coaxial cable
system must be terminated with
75Ćohm terminating loads attached to
the taps located at both ends of the
cable system. This minimizes the
signal reflections that could interfere
with other signals transmitted on the
cable. The terminating load consists of
a BNC plug connector and an internal
75Ćohm resistor.
BNC JackĆtoĆJack Adapter
The BNC jackĆtoĆjack inĆline splicing
adapter is recommended for making
cable splices when the length of a
cable must be extended (for example,
when a new drop is added).
3.3.2 Selecting the Cable Type
The number of drops that can be connected to the network varies
depending upon the cable type and length. Figure 3.5 shows some
representative distances and the maximum number of physical drops
allowed.
30
35
40
45
50
55
0 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000
RG Ć 59/U =
RG Ć 11/U =
P
H
Y
S
I
C
A
L
D
R
O
P
S
NETWORK LENGTH (FEET)
Figure 3.5 Ć Representative Racks vs. Network Length
To calculate the maximum number of drops, use the following
formulas:
For Beldenr 9259 (RGĆ59/U): N = 52 Ć 0.725*X
For Belden 8213 (RGĆ11/U): N = 52 Ć 0.425*X
where: Nă=ămaximum number of drops
Xă=ăcable length in hundreds of feet
The RGĆ59/U and RGĆ11/U cables can be mixed in a network
application. For example, RGĆ59/U cabling may be used inside a