Cabletron Systems STHI manual B.2 Shielded Twisted Pair STP, B.2.1 STP Cable Categories

Shielded Twisted Pair (STP)

Table B-2. UTP Maximum Lobe Lengths.

	@ 4 Mbps		@ 16 Mbps
UTP
Category	meter	(feet)	meter	(feet)
	s		s
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

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

30.5dB. 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.

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