SKILLCERTPRO
Unshielded twisted pair—UTP Ethernet cable uses two or four pairs of copper wire. The
twist in the wires reduces electromagnetic interference.
568A/B—Ethernet cables are terminated with RJ-45 connectors. The pin-out (which wire
connects to which pin) of those connectors is defined in the EIA/TIA 568A & 568B Standards.
The difference between 568A and 568B is that the transmit and receive pairs are reversed.
This allows for two types of cables, straight-through and crossover.
Straight-through is used to connect a device to the network via a switch or hub. It uses the
same pin-out on both ends, whether 568A or 568B. A crossover cable is used to connect
one device directly to another, such as two computers, without a switch or hub between
them. Crossover cables use 568A on one end and 568B on the other.
Fiber
Fiber optic cable uses light pulses to transmit data through a glass or plastic core. The cable
consists of four layers. The core is surrounded by a cladding that refracts light back into the
core. The other two layers are the outer sheath, the part you see, and a strength member
or buffer to protect the fiber.
Fiber is not subject to electromagnetic interference, since it uses light to transmit data.
Transmission distances are longer and data rates are higher on fiber than they are on
copper cable. There are two basic types of fiber, single-mode and multimode. Single-mode
fiber carries only one light path, typically sourced by a laser. Multimode carries multiple
light paths and is sourced by an LED. Single-mode has a much longer transmission distance
than multimode.
Coaxial
Coaxial cable is used primarily for cable Internet service and audio/video applications such
as cable TV. It has a single copper conductor core surrounded by a dielectric insulator and
one or more layers of shielding. The shielding reduces electromagnetic interference. The
two most common types of coaxial cable are RG-6 for data and RG-59 for audio/video.
Speed and Transmission Limitations
Each type of network has speed and distance limitations.
Category 5 cable supports data rates up to 100 Mbps.
Category 5e cable supports data rates up to 1 Gbps.
Category 6 cable supports data rates up to 10 Gbps up to 55 meters and 1 Gbps up to 100
meters.
The most commonly used fiber is multimode and supports data rates up to 100 Mbps up to
2000 meters, 1 Gbps up to 550 meters, and 10 Gbps up to 300 meters.
Video Cables
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