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2-8 CHAPTER 2: OVERVIEW
Auxiliary Power. Auxiliary +5 volt power is available on the STP
connector for specialty powered MAUs, powered port expanders, or
signal conversion devices such as token ring STP-to-fiber optic
transceivers. To use the auxiliary power pins, follow the guidelines in
Table 2-4.
3Com does not guarantee compatibility with external devices that use
the auxiliary power pins of the STP connector. Consult the
manufacturer of external devices to ensure compliance with the
maximum current allowed and to ensure the device does not
compromise STP token ring signalling.
Cabling Standards
Cabling should be installed in accordance with the following standards:
■ EIA/ TIA-568 – Commercial building telecommunications wiring
standard
■ TSB-36 – Additional cable specifications for unshielded twisted pair
cables
■ IBM cabling guidelines
Table 2-5 summarizes the maximum number of workstations supported
on a token ring network.
Ports on active retimed MAUs usually count as one “station.” If your
device is plugged into an active retimed MAU, the device and the MAU
port total two “stations.” For example, a token ring with all active
retimed MAUs will support a total of 125 devices with STP cabling. A
token ring with all passive MAUs will support a total of 250 devices
with STP cabling. Check the documentation for your MAU for port and
ring in/out station equivalencies.
Table 2-4 Auxiliary Pin Use
Pinout (STP) Maximum Current
Pin 3 +5 volts (+/- 10%), 500 mA (fused at 2.5 A)
Pins 2, 4, 7, 8 Ground pins
Table 2-5 Maximum Workstations on a Token Ring Network
Cable Type Token Ring Speed 4 Mbps Token Ring Speed 16 Mbps
STP 250 stations 250 stations
UTP 144 stations 250 stations
SS2TRHWBook Page 8 Monday, May 5, 1997 3:11 PM