Cabletron Systems NBR-420 - Manual (Page 64)

Appendix C: Network Planning and Configuration
Page C-2 NBR-SERIES Installation Guide
• Insertion Loss - Between frequencies of 5.0 and 10.0 MHz, the
maximum insertion loss must not exceed 11.5 dB. 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
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. You can also use shielded twisted pair cables,
such as IBM Type 1 cable, but keep in mind that this cable has an
impedance of 150 ohms. The high impedance of the IBM Type 1 cable
increases signal reflection. However, due to cable shielding, and its
subsequent lack of crosstalk between shielded pairs, this signal
reflection has little effect on the quality of the received signal.
• Jitter - Intersymbol interference and reflections can cause jitter in the
bit cell timing, resulting in data errors. 10BASE-T links must not
generate more than 5.0 ns of jitter. Make sure your cable meets
10BASE-T link impedance requirements to rule out jitter as a concern.
• Delay - The maximum propagation delay of a 10BASE-T link segment
must not exceed 1000 ns. This 1000 ns maximum delay limits the
maximum link segment length to no greater than 200 meters.
• Crosstalk - Signal coupling between different cable pairs within a
multi-pair cable bundle causes crosstalk. 10BASE-T transceiver
design alleviates concerns about crosstalk, providing the cable meets
all other requirements.
• Noise - Crosstalk, or externally induced impulses, can cause noise.
Impulse noise may cause data errors if the impulses occur at very
specific times during data transmission. Generally, noise is not a
concern. If you suspect noise-related data errors, you may need to
reroute the cable or eliminate the source of the impulse noise.
NOTE
Losses introduced by connections at punch-down blocks and
other equipment reduce total segment length. For each
connector or patch panel in the link, subtract 12 meters from
the total length of your cable.