J-1
The IDNet cabling requirements are detailed in Chapter 7 of this manual.
Line Characteristics
Note: In the following paragraphs the term "MAPNET channel" is used to mean those
lines connected to any one Mapnet Transceiver board. Parallel runs from the same board
do not constitute separate channels. The term "continuous run" refers to the loop distance
from the primary output, through all devices and back to the secondary output.
Line characteristics are based on 0.58uF and/or 35 Ohms total line resistance.
Total length of line on one MAPNET channel shall not exceed 3,000 m including all
T-taps and parallel runs.
Maximum length for ONE continuous MAPNET run is 1200 m for up to 128 MAPNET
devices using 1.5 mm sq cable.
When the run exceeds 850 m it is necessary to use twisted, shielded pair.
Copper Line Characteristics
Network "Wired" (formerly called RS-485) Communication wiring must be 0.75 mm sq
twisted, shielded pair (TSP), or 0.22 mm sq twisted pair (TP). Shielded Cable is
recommended for new installations. When shielding is used, the shield shall be connected
to Earth Ground, at the Left Port end of span only.
No T-tapping of the Network conductors is allowed. Network wiring is point-to-point,
only.
Maximum line length between ports at 57,600 and 9600 bits per second is shown in the
table below.
Table J- 1 Network: Maximum Transmission Distances, "Wired" Network
Maximum Wiring Distance
Communication Speed
0.75mm sq TSP Wire.
(Maximum capacitance
between conductors is 174
pf. per meter)
0.22mm sq TP Wire.
(Maximum capacitance
between conductors is 66
pf. per meter)
57,600 bps 3,000 m 2,300 m
9600 bps 5,600 m 4,000 m
Continued on next page
Appendix J
Cable Characteristics
IDNet
4100 MAPNET II
NETWORK
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