Cabletron Systems CXRMIM, Installation Manual

Page: 21 / 78

NETWORK CABLE REQUIREMENTS
Installation Guide 2-3
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.
Temperature
Multi-pair PVC 24 AWG telephone cables typically have an attenuation of
approximately 8 to 10 dB/100m at 20
°
C (68
°
F). The attenuation of PVC
insulated cable varies significantly with temperature. At temperatures greater
than 40
°
C (104
°
F), we strongly recommend that you use plenum-rated cables to
ensure that cable attenuation remains within specification.