REQUIREMENTS/SPECIFICATIONS
Table 2-3. Maximum Cable Attenuation
4.0 MHz
STP (IBM Types 1 & 2) 22 dB/km
STP (IBM Types 6 & 9) 33 dB/km
16.0 MHz
45 dB/km
66 dB/km
2.1.4 Impedance
The characteristic impedances for specific cable types are listed in
Table 2-4. These are typical impedances, and can vary among different manufacturers of cabling.
Table 2-4. Cable Impedance
Cable Type Characteristic Impedance
STP (IBM Types 1 & 2) 150 ohms (1 MHz to 20 MHz)
±
10%
STP (IBM Types 6 & 9) 150 ohms (1 MHz to 20 MHz)
±
10%
2.1.5 Crosstalk
Crosstalk is caused by signal coupling between the different cable pairs contained within a multi-pair cable bundle. In shielded twisted pair cables, the effects of crosstalk are minimized.
2.1.6 Maximum Number of Stations
Table 2-5 shows the maximum number of stations that can be inserted into a single ring using STP cabling according to ring speed.
Table 2-5. Maximum Number of Stations
4 Mbit/sec 16 Mbit/sec
Number of Stations 250 stations 136 stations
NOTE: If unshielded twisted pair (UTP) cabling is used with
STP in the same ring, the number of stations is determined by the UTP specification.
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