Cabletron Systems SEHI100TX manual UTP Cable Specifications

Chapter 3: Installation Requirements and Specifications

3.1.2UTP Cable Specifications

The device at the other end of the twisted pair segment must meet IEEE 802.3u 100BASE-T specifications. When connecting a 100BASE-TX Twisted Pair Segment to the SEHI twisted pair network ports and the EPIM-100TX module, the network must meet the following requirements:

Length

The IEEE 802.3u 100BASE-T standard requires that 100BASE-TX devices be capable of transmitting over a 100 meter (328 foot) link using Category 5 UTP wire.

Impedance

UTP cables typically have an impedance of between 85 to 110 ohms.

Jitter

Intersymbol interference and reflections cause jitter in the bit cell timing, resulting in data errors. A 100BASE-TX link must not generate more than

1.4ns of jitter. If the cable meets the impedance requirements for a 100BASE-TX link, jitter should not be a concern.

Crosstalk

Crosstalk is caused by signal coupling between the different cable pairs contained within a multi-pair cable bundle. 100BASE-TX transceivers are designed so that the user does not need to be concerned about cable crosstalk, provided the cable meets all other requirements.

Noise

Noise is caused by either crosstalk or externally induced impulses. Impulse noise may cause data errors if the impulses occur at very specific times during data transmission. Generally, the user need not be concerned about noise. If noise-related data errors are suspected, it may be necessary to either reroute the cable or eliminate the source of the impulse noise.

3-2 SEHI100TX User’s Guide