Chapter 3 System Configuration
3-5
(Example)
L (thin): 2 m + 2 m + 2 m + 25 m + 6 m
= 37 m
L (thick): 70 m + 125 m
= 195 m
From Table 3.4:
195 + (5 x 37) = 380 m
<
500 m
⇒
125 Kbits/s OK
195 + (2.5 x 37) = 287.5 m
>
250 m
⇒
250 Kbits/s Not allowed
195 + 37
= 232 m
>
100 m
⇒
500 Kbits/s Not allowed
From the result of the calculations above, it is determined that it is only possible to communicate at 125
kbps with this configuration.
Even if the above conditions are met, however, the current that flows in each cable must not exceed the
maximum current capacity of each cable.
[3] Restrictions on drop line length
The drop line length refers to the length from the beginning of the drop line to the position in the drop
line farthest away from the trunk line.
The maximum drop line length is 6 m.
(Example)
2 m from Device Tap A to device A
4 m from Device Tap A to device B
6 m from Device Tap A to device C
Thick (70 m)
Device Tap Device Tap
Device
Device
Device
Device Tap
(Note)
(Note) With a terminal resistor
Thin (25 m)
Thick (125 m)
Thin (6 m)
Device
Device
Device
(Note)
Device
Thin (2 m) Thin (2 m) Thin (2 m)
Device Tap
Device
Trun
k
Trunk
Device Tap
Drop line 6 m
Device A
Device Tap
Device Tap
Trunk
Trunk
Device Tap A
Device Tap
Device B
Device C
Drop line 1 m
Drop line
2 m
Drop line
2 m
Drop line 1 m
