Table 4: SA Bus rules
Category
Rules/limits
365 m (1,198 ft) maximum bus length.
152 m (500 ft) maximum between an NS network sensor and the
bus supervisor FEC or VMA supplying power to the sensor) using
bus cable connected to the SA Bus screw terminal blocks.
30 m (98 ft) maximum length for network sensors using bus cables
connected to the 6-pin modular jack (6-Pin SA Bus port).
366 m (1,198 ft) maximum Bus Length.
Cable length for SA Bus
1.5 m (5 ft) maximum between the network engine and DIS1710
Local Controller Display.
Recommended bus cable
type
Screw Terminal Connections
: 0.6 mm (22 AWG) Stranded 4-wire, 2-
Twisted Pairs, Shielded Cable for screw terminals.
Modular Jack Connections
: 6-Pin Modular Connectors with 24 or
26 AWG 6-Wire, 3 Twisted-Pairs.
EOL termination on the SA
Bus
Each SA Bus supervisor has integral (fixed ON) EOL termination,
which typically provides sufficient EOL termination on a SA Bus.
Long SA Bus runs or persistent communication problems on a SA
Bus may require EOL termination at the last device on the SA Bus in
addition to the integral EOL termination at the SA Bus supervisor)
All NCE25 models are SA Bus supervisors.
N2 Bus rules
The N2 Bus connects N2 controllers to specified NCE25 models. NCE251x models support a single
N2 Bus trunk with up to 32 N2 devices.
Observe the rules in the following table when designing and installing the connected N2 Bus.
Table 5: N2 Bus rules
Category
Rules/maximums allowed
One N2 trunk supported (on NCE251x models only).
General
Only daisy-chained devices (with maximum stub length of 3 m [10
ft] to any device).
Number of N2 devices
supported
Up to 32 N2 devices supported on the N2 trunk.
1,500 m (4,921 ft) twisted pair cable.
Cable length and type
2,000 m (6,561 ft) between two fiber modems.
Cable
Solid or stranded 1.0 mm (18 AWG) 3-wire is recommended. Solid
or stranded 0.5 mm (24 AWG) larger 3-wire or 4-wire (two twisted-
pairs) is acceptable.
Note:
Ensure the + and - bus leads are a twisted pair. On
applications using 4-wire (two twisted-pairs) cable, isolate and
insulate unused conductor.
Bus termination
N2 devices are self-terminating and have no EOL setting.
NCE25 Installation Instructions
10