Installation manual

57
Appendix A
UTP Reference
UTP Wiring Specifications
10BASE-T requires UTP wiring capable of supporting 10 Megabit data
rates. Use Level 3 or better UTP wiring throughout the 10BASE-T wiring
system. The wire should be 22 to 26 AWG, 100 Ω impedance with 3 to 8
twists per foot. Typically, if a cable is flat, the pairs are untwisted and will
cause problems. A cable more or less round in section is likely to be
twisted.
The specifications of 6 common modular cables and their applicability to
10BASE-T network use are shown in Table 7. The maximum length for
10BASE-T UTP segments is 100 meters (328 ft.).
Table 7: Usable and Unusable Twisted Pair Cable
Cable
Level
Cable Description AC Character Specification
Twist/
Foot
10BASE-T
OK?
1 Unshielded untwisted N/A CCITT N/A NO!
2 Individual UTP 100 Ω ± 30 Ω RS232 1BASE5
AT&T PDS
N/A NO!
3 Typical Individual UTP 100 Ω ± 15 Ω TI, AT&T ISDN
10BASE-T
IBM Type 3
3-5 YES
4 Enhanced Individual
UTP
100 Ω ± 30 Ω EIA, TIA
10BASE-T
NEMA
5-8 YES
5 Individual STP 100 Ω ± 30 Ω EIA, TIA
10BASE-T
8-10 YES
IBM
Type 1
Individual STP 150 Ω PCC FT 1 N/A NO!