Hitachi HIDIC EH-150 Applications Manual page 21

(Example)
Device
(Note)
Thin (2 m)
Thin (2 m)
Device Device
L (thin): 2 m + 2 m + 2 m + 25 m + 6 m
L (thick): 70 m + 125 m
From Table 3.4:
195 + (5 x 37) = 380 m
195 + (2.5 x 37) = 287.5 m > 250 m ⇒ 250 Kbits/s Not allowed
195 + 37 = 232 m
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)
k
Trun
Device Tap
Device
Thin (25 m)
Thin (2 m)
Device
= 195 m
< 500 m ⇒ 125 Kbits/s OK
> 100 m ⇒ 500 Kbits/s Not allowed
Trunk
Device Tap
Drop line 6 m
Thick (125 m)
Thick (70 m)
Device Tap
Device Tap
Device Device
= 37 m
Trunk
Device Tap A
Device Tap
Drop line 1 m
Device Tap
Device Tap
Drop line
2 m
Drop line 1 m
Device A
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
3-5
Chapter 3 System Configuration
Device Tap
(Note)
Thin (6 m)
Device
(Note) With a terminal resistor
Trunk
Drop line
2 m
Device B Device C