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Shielded Twisted Pair (STP)
Page B-3
Some UTP category 3 cables fail to meet the performance minimums
required to support a Token Ring network. Whereas category 3 allows for
near end crosstalk (NEXT) loss as low as 23 dB per 100 m at 16 Mbps,
Token Ring performance requirements demand a NEXT loss of at least
30.5 dB. To safeguard against worst case conditions (running at 16 Mbps
and using category 3 cable with the category’s lowest qualifying NEXT
loss—23 dB), the recommended maximum lobe length should be reduced
to keep crosstalk interference within acceptable levels.
B.2 Shielded Twisted Pair (STP)
STHI models 42 and 44 and TPIM models T1 and T4 support all STP cables
classified as IBM Types 1, 2, 6, and 9, all of which meet Token Ring
network performance requirements.
B.2.1 STP Cable Categories
The supported STP cable types meet the following specifications:
IBM Type 1 consists of two shielded twisted pairs (STP) of 22 AWG solid
wire for data. Used for the longest cable runs within the walls of buildings.
IBM Type 2 consists of six pairs of unshielded twisted pairs of 24 AWG
solid wire and a shield casing. The two pairs carried within the shield
casing are used to carry Token Ring data. The four pairs carried outside of
the shield casing are typically used for voice communication. Type 2 is
frequently used to wire cable runs within the walls of buildings.
Table B-2. UTP Maximum Lobe Lengths.
UTP
Category
@ 4 Mbps @ 16 Mbps
meter
s
(feet)
meter
s
(feet)
3 200 (656) 100* (328)*
4 225 (738) 110 (360)
5 250 (820) 120 (393)
* for cable with NEXT loss ≥ 30.5 dB per 100m