Allied Telesis AT-2450 Series Guía de instalación descargar pdf (Pagina 34)

AT-2450 PCI Ethernet Adapter Card

Important 10BASE-T Cable Considerations. There are various

grades of voice-quality and data-quality cables available. The five

common modular cable specifications and their applicability to

10BASE-T network use are shown in Table 5.

These can appear to be similar externally, and their DC

characteristics are also similar, although their AC characteristics,

and therefore high-speed data transmission characteristics, are

radically different. As a rule of thumb, if a cable type is flat, it is

typically untwisted, and will cause problems. If a cable is more or

less round in section, it will typically work.

If any voice-quality cabling is used in a 10BASE-T network, data

movement is slow, collision-prone, or non-existent. The LNK

indicator on the interface will usually indicate a valid link in such

a case. Be sure that all cabling used with the 10BASE-T adapter

Table 5: Usable and Unusable 10BASE-T Cable

Cable

Level

Cable

Description

Char.

Speciﬁ-

cation

Twist/

Foot

10BASE-T

OK?

Unshielded

untwisted

N/A CCITT none NO!

Unshielded

Indv.Twisted Pairs

100 Ω

±30 Ω

RS232 1BASE5

AT&T PDS

none NO!

Typ. Unshielded

Indv. Twisted Pairs

100 Ω

±15 Ω

TI, AT&T ISDN

10BASE-T

IBM Type 3

3-5 YES

Unshielded

Enhanced Indv.

Twisted Pairs

100 Ω

±30 Ω

EIA, TIA

10BASE-T

NEMA

5-8 YES

Shielded

Indv. Twisted Pairs

100 Ω

±30 Ω

EIA, TIA

10BASE-T

8-10 YES

2450T IG.bk Page 28 Tuesday, December 29, 1998 11:58 AM

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Allied Telesis AT-2450 Series Guía de instalación Pagina 34

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