3Com 52x Cabling Standards, 4Auxiliary Pin Use, 5Maximum Workstations on a Token Ring Network

2-8CHAPTER 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.

Table 2-4Auxiliary 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

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.

Table 2-5Maximum 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

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.