Transmission Media - Computer Networks

What is a transmission medium?

A transmission medium can be broadly defined as anything that can carry information from a source to a destination

Name the two main categories of transmission media

Guided (Wired) and Unguided (Wireless)

Give three examples of guided transmission media

Twisted pair cable, coaxial cable and fiber optics cable

Name three unguided (wireless) transmission media

Radio wave, microwave and infrared

What are guided media?

Guided media are those who provide a conduit from one device to another. Eg twisted pair cable, coaxial cable and fiber-optic cable. A signal traveling along any of these media is directed and contained by the physical limits of the medium.

Twisted-pair and coaxial cable use __________ that accept and transport signals in the form of ________

metallic (copper) conductors, electric current

_________ is a cable that accepts and transports signals in the form of light

Optical fiber

Describe Twisted-Pair Cable

A twisted pair consists of two conductors (normally copper), each with its own plastic insulation, twisted together

[Twisted Pair] One of the wires is used to carry signals to the ________, and the other is used only as a _________

receiver, ground reference

[Twisted Pair] In addition to the signal sent by the sender on one of the wires, _________ and ________ may affect both wires and create unwanted signals

interference (noise), crosstalk

By twisting the pairs, __________

a balance is maintained.

The number of ________ per unit of length has some effect on the quality of the _____

twists, cable

STP cable has a _________

metal foil or braided mesh covering that encases each pair of insulated conductors

The most common UTP connector is ____

RJ45

One way to measure the performance of twisted-pair cable is to compare _____ versus ______ and _______

attenuation, frequency, distance

Twisted-Pair cables are used in ________ lines to provide voice and data channels

telephone

A fiber-optic cable is made of _______ or ________ and transmits signals in the form of _________

glass, plastic, light

Name the advantages of the fiber optic cable

• Higher bandwidth

• Less signal attenuation

• Immunity to electromagnetic interference

• Resistance to corrosive materials

• Light weight

• Greater immunity to tapping

Name the disadvantages of the fiber optic cable

• Installation and maintenance

• Unidirectional light propagation.

• Cost

Unguided medium transport ____________ without using a physical conductor

electromagnetic waves

What’s the range of VHF band?

3-30 kHz

What’s the range of LF band?

30 - 300 kHz

What’s the range of MF band?

300 kHz - 3 MHz

What’s the range of the HF Band?

3 - 30 MHz

AM Radio is an application of ____ band

MF (Middle Frequency) Band

An application of EHF Band is _____

radar, satellite

Electromagnetic waves ranging in frequencies between 1 and 300 GHz are called _________

microwaves

Electromagnetic waves ranging in frequencies between 3j-hz and 1 GHz are called _________

radio waves

Radio waves, for the most part, are _______. When an antenna transmits radio waves, they are propagated in all directions.

omnidirectional

What’s the disadvantage of radio waves’ omnidirectional property?

The radio waves transmitted by one antenna are susceptible to interference by another antenna that may send signals using the same frequency or band

Radio waves are good candidates for long-distance broadcasting such as _____

AM radio

Radio waves, particularly those of ______ and ______ frequencies, can penetrate walls

low, medium

Infrared waves, with frequencies from ______ can be used for ________ communication.

300 GHz to 400 THz, short-range