GarrettCom 14E - Manual (Page 47)

Magnum14E Media Converters Installation and User Guide (10/02)
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allowable maximum cable distance vs. TP cable without the 14Es.
Consider a more typical use of Magnum 14Es in a shared Fast Ethernet segment. A
stack of Fast Ethernet hubs comprises the only repeater in the collision domain, and the users
and servers in the local workgroup are each connected via Category 5 twisted pair cable, a
maximum of 30 meters (100 ft.) in length. It is desired to connect one remote user with a fiber
NIC via fiber cable, using a Magnum 14Es in the circuit. How long can the fiber cable be?
The solution is :
512 = total available Bit Times in a collision domain diameter,
minus 100 BT for two DTEs on each end leaves 412 BTs,
minus 90 BT for one Class II stackable repeater leaves 322 BTs,
minus 30 BT for one 30-meter TP cable from hub to user node leaves 292 BTs,
minus 5 BT for a short TP cable from the hub to 14E leaves 287 BTs,
minus 20 BT for one Magnum 14E leaves 267 BTs for fiber cable,
which indicates a fiber cable length of about 260 meters.