|  | 8.5 | Planning Structured Cabling: Horizontal and Backbone Cabling
| 8.5.1 | Catchment area problems

If the 100 m catchment area of a simple star topology wiring closet cannot provide enough coverage for all the devices that need to be networked, the star topology can be extended by using repeaters. Their purpose is to avoid the problem of signal attenuation, and are called hubs. Generally speaking, when repeaters, or hubs, are used in this manner, they are located in additional wiring closets called IDFs. These IDF closets are linked by networking media to a central hub located in another wiring closet called the MDF. TIA/EIA-568-A specifies the use of one of the following types of networking media:

- 100 Ohm UTP (four pair)
- 150 Ohm STP-A (two pair)
- 2 fiber (duplex) 62.5/125 µm optical fiber
- multimode optical fiber

The TIA/EIA recommends the use of CAT 5 UTP for horizontal cabling, when an Ethernet LAN uses a simple star topology.

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