Transmission Media

Communication media in which signals are linked with any physical conductor cable. Data signals are bounded in a cable, hence also called bounded media.

There are 3 types of guided media:

• Twisted Pair Cable
• Coaxial Cable
• Fibre Optics Cable

1.1 Twisted Pair Cable

Consists of pair of  copper wires (~1mm thickness) insulated with plastic or rubber. The wires are twisted together to reduce electrical interference (crosstalk).

Commonly used in local telephone communication and fast data transmission.

Two types:

• UTP — Unshielded Twisted Pair
• STP — Shielded Twisted Pair

Categories:

Category	Speed (Mbps)	Use
CAT5	100	LAN
CAT5E	125	LAN
CAT6	200	LAN
CAT7	600	LAN

Connectors used in Twisted Pair Cable:

• Registered Jack (RJ-11) — 4 wires (2 pairs) → used for Telephone
• RJ-45 — 8 wires (4 pairs) → used for CPU, Ethernet

1.2 Coaxial Cable

Also known as coaxiale cable or ethernet cable (grey). Consists of:

• Inner conductor (~1.5mm thickness)
• Insulator applied on top of it
• Copper mesh / outer conductor
• Outer jacket made of plastic or rubber

Widely used for cable television industry and fast data transmission such as Ethernet.

Categories:

Type	Use
RG-59	Cable TV
RG-58	Ethernet, CCTV
RG-11	Ethernet

Connectors:

• BNC — Bayonet Neil Concelman
• BNC-T
• BNC Terminator

1.3 Fibre Optics Cable

Made up of glass and plastic that transmit signals in the form of light. The inner part is made of glass, known as the core. The core is surrounded by a concentric layer of glass called cladding. The cladding is further protected by a plastic outer jacket.

Key Properties:

• Can handle much higher bandwidth than copper
• Fibre does not leak light and has no resistance
• Can transfer data at long distances
• Very expensive and difficult to maintain/install

Connectors:

• SC — Subscriber Channel (Cable TV)
• ST — Straight Tip (Ethernet)
• MTRT — Mechanical Transfer Jack

Transports data through electromagnetic waves without using any physical conductor. Often referred to as wireless communication. Unguided signals travel from source to destination by 3 bases:

• Microwave
• Radiowave
• Infrared

2.1 Radiowave

Electromagnetic waves having frequency between 3 KHz – 1 GHz are known as radiowaves.

Key Properties:

• Omnidirectional — can travel in any direction from source
• Can penetrate walls easily
• Propagation is ground and sky based

Examples: Cell phone, Bluetooth, Wi-Fi

2.2 Microwave

Electromagnetic waves having frequency between 1 GHz – 300 GHz are known as microwaves.

Key Properties:

• Unidirectional — travels from source to destination in a line of sight
• Cannot penetrate walls, but lower frequencies are partially able to

Two types of microwave communication:

• Terrestrial Communication
• Satellite Communication

2.3 Infrared Waves

Electromagnetic waves having frequency between 300 GHz – 400 THz are known as infrared waves. Also called millimeter waves.

Key Properties:

• Unidirectional and uses line of site propagation
• Cannot penetrate walls due to very high frequency

Example: TV remote — uses infrared connection for door-like remote communication.

Media Type	Medium	Frequency / Speed	Key Feature	Example Use
Twisted Pair	Physical	100–600 Mbps	Low cost, twisted to reduce interference	LAN, Telephone
Coaxial Cable	Physical	Higher than TP	Layered structure, shielded	Cable TV, CCTV
Fibre Optics	Physical / Light	Very high (Gbps+)	No resistance, long distance	Internet backbone
Radiowave	Wireless	3 KHz – 1 GHz	Omnidirectional, penetrates walls	Wi-Fi, Bluetooth
Microwave	Wireless	1 GHz – 300 GHz	Line of sight, high speed	Satellite, Terrestrial
Infrared	Wireless	300 GHz – 400 THz	Very short range, no wall penetration	TV Remote