Cabletron Systems STHI Manual De Usuario

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.

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.

The supported STP cable types meet the following specifications:

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.

 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.

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