Digital Equipment DEC WANrouter 90, Руководство пользователя, Страница: 42 / 121

2–5 Preparing for Installation
Table 2–1: Maximum Cable Lengths — Router to Devices
Line Protocol Data Rate (b/s) Cable Length
EIA-232-D/V.24
RS-423-A
RS-422-A
V.35
15 m (50 ft)
1200 m (4000 ft)
150 m (500 ft)
58 m (190 ft)
25 m (80 ft)
1200 m (3900 ft)
60 m (200 ft)
Up to 20 K
Below 4.8 K
20 K
48 K
64 K
Up to 64 K
48 K
Table 2–1 assumes the following:
•
The V.24 cable capacitance is 50 pF/ft.
•
The RS-423-A cable capacitance is 15 pF/ft.
•
The RS-422-A cable is 100 ohm terminated with a capacitance of 15 pF/ft .
The maximum cable length for V.35 is a recommended figure only.
2.3.3.2 ThinWire Ethernet Connection
If you are installing the DEC WANrouter 90 in a standalone configuration, ensure
that the following requirements are met:
•
The maximum ThinWire cable segment length must not exceed 185 m
(606 ft).
•
There must be a 50-ohm terminator at each end of the cable segment unless
the cable ends in a DEMPR or DESPR (both these devices have inbuilt
50-ohm terminators).
•
There must be only one ground per cable segment.
•
There must be at least 0.5 m (19 in) between T-connectors.
•
The maximum number of stations, between terminators, must not exceed 30.