It may not be possible, however, to run a cable between two buildings on different sides of a public road, and it is certainly a major undertaking when the buildings are located on different continents. Such conditions may call for use of unbounded media. Bandwidth , the range of frequencies that the cable can accommodate. LANs generally carry data rates of 1 to 100 megabits per second and require moderately high bandwidth. Attenuation describes how cables reduce the strength of a signal with distance.
Resistance is one factor that contributes to signal attenuation.
Electrical magnetic interference , or EMI , can be a major headache for LAN technicians. Many electrical devices generate magnetic fields that produce unwanted electrical currents in data cables. The noise that results from these currents can degrade data signals, sometimes stopping communication altogether due to excessive error rates. Electrical motors and fluorescent lights are common sources of EMI, and it can be a genuine challenge to cable a network in environments such as factories that contain many electrical devices. Solid conductors are preferred for permanent wiring, but stranded conductors make the cable more flexible and easier to connect to equipment.