Cabletron Systems SEHI-32 - Manual (Page 16)

INSTALLATION REQUIREMENTS/SPECIFICATIONS
Page 2-2
2.1.2 UTP and STP Cable Specifications for the Network Ports
and EPIM-T Module
The device at the other end of the twisted pair segment must meet
IEEE 802.3 10BASE-T specifications. When you connect a 10BASE-T
Twisted Pair Segment to the SEHI’s 10BASE-T Twisted Pair Network
Ports and EPIM-T module, your network must meet the following
requirements:
Length
The IEEE 802.3 10BASE-T standard requires that 10BASE-T devices
transmit over a
100 meter (328 foot) link using 22-24 AWG unshielded
twisted pair wire. However, cable quality largely determines
maximum link length. If you use high quality, low attenuation cable,
you can achieve link lengths of up to 200 meters. Cable delay limits
maximum link length to 200 meters, regardless of the cable type.
Insertion Loss
The maximum insertion loss allowed for a 10BASE-T link is 11.5 dB
at all frequencies between 5.0 and 10 MHz. This includes the
attenuation of the cables, connectors, patch panels, and reflection
losses due to impedance mismatches in the link segment.
Impedance
Cabletron Systems 10BASE-T Twisted Pair products will work on
twisted pair cable with 75 to 165 ohms impedance. Unshielded twisted
pair cables typically have an impedance of between 85 to 110 ohms.
Shielded twisted pair cables, such as IBM Type 1 cable, can also be
used. You should remember that the impedance of IBM Type 1 cable is
typically 150 ohms. This increases the signal reflection caused by the
cable, but since the cable is shielded, this signal reflection has little
effect on the received signal’s quality due to the lack of crosstalk
between the shielded cable pairs.
Jitter
Intersymbol interference and reflections can cause jitter in the bit cell
timing, resulting in data errors. A 10BASE-T link must not generate
more than 5.0 nsec. of jitter. If your cable meets the impedance
requirements for a 10BASE-T link, jitter should not be a concern.