Transmission media use wire or cable to send communications signals
Answers
Answer:
Explanation:
transmission media may be of two types −
Guided − In guided media, transmitted data travels through cabling system that has a fixed path. For example, copper wires, fibre optic wires, etc.
Unguided − In unguided media, transmitted data travels through free space in form of electromagnetic signal. For example, radio waves, lasers, etc
Twisted Pair Cable
Copper wires are the most common wires used for transmitting signals because of good performance at low costs. They are most commonly used in telephone lines. However, if two or more wires are lying together, they can interfere with each other’s signals. To reduce this electromagnetic interference, pair of copper wires are twisted together in helical shape like a DNA molecule. Such twisted copper wires are called twisted pair. To reduce interference between nearby twisted pairs, the twist rates are different for each pair.
Shielding twisted pair cable
To counter the tendency of twisted pair cables to pick up noise signals, wires are shielded in the following three ways −
Each twisted pair is shielded.
Set of multiple twisted pairs in the cable is shielded.
Each twisted pair and then all the pairs are shielded.
Such twisted pairs are called shielded twisted pair (STP) cables. The wires that are not shielded but simply bundled together in a protective sheath are called unshielded twisted pair (UTP) cables. These cables can have maximum length of 100 metres
. Coaxial Cable
Coaxial cables are copper cables with better shielding than twisted pair cables, so that transmitted signals may travel longer distances at higher speeds. A coaxial cable consists of these layers, starting from the innermost −
Stiff copper wire as core
Insulating material surrounding the core
Closely woven braided mesh of conducting material surrounding the insulator
Protective plastic sheath encasing the wire
Coaxial cables are widely used for cable TV connections and LANs.
Optical Fibre
Thin glass or plastic threads used to transmit data using light waves are called optical fibre. Light Emitting Diodes (LEDs) or Laser Diodes (LDs) emit light waves at the source, which is read by a detector at the other end. Optical fibre cable has a bundle of such threads or fibres bundled together in a protective covering
Answer:
phisical
Explanation:
physical transmission media use wire or cable to send communications signals.