Enterasys Networks BRIM-E6 User Manual
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APPENDIX B: EPIM CABLE REQUIREMENTS
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BRIM-E6 USER’S GUIDE
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.
Delay
The maximum propagation delay of a 10BASE-T link segment must not
exceed 1000 nsec. This 1000 nsec. maximum delay limits the maximum
link segment length to no greater than 200 meters.
Crosstalk
Crosstalk is caused by signal coupling between the different cable pairs
contained within a multi-pair cable bundle. 10BASE-T 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 can be 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.