A type of cable that consists of two independently insulated wires twisted around one another. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction.

While twisted-pair cable is used by older telephone networks and is the least expensive type of local-area network (LAN) cable, most networks contain some twisted-pair cabling at some point along the network.

Twisted Pair Cable

Coax consists of a center wire surrounded by insulation, which is in turn surrounded by an outer conductor of braided wire that serves as a grounded shield, enclosed in an outer jacket of insulation. The shield minimizes electrical and radio frequency interference.

Coax gets its name because its two channels run concentrically along the same axis. It's quite an old product, originally designed to carry analog telephone signals at high capacity with little electronic noise. It's also a preferred product, virtually weatherproof and much more durable than "twinlead," the old-fashioned flat wire originally used for TV. Signal performance is also superior. Coax doesn't pick up unwanted signals, and it's not affected by contact with metal structures.

About Coax

Fiber optic cabling consists of a center glass core surrounded by several layers of protective materials. It transmits light rather than electronic signals eliminating the problem of electrical interference. This makes it ideal for certain environments that contain a large amount of electrical interference. It has also made it the standard for connecting networks between buildings, due to its immunity to the effects of moisture and lighting.

Fiber optic cable has the ability to transmit signals over much longer distances than coaxial and twisted pair. It also has the capability to carry information at vastly greater speeds. This capacity broadens communication possibilities to include services such as video conferencing and interactive services. The cost of fiber optic cabling is comparable to copper cabling; however, it is more difficult to install and modify.

The center core of fiber cables is made from glass or plastic fibers. A plastic coating then cushions the fiber center, and kevlar fibers help to strengthen the cables and prevent breakage. The outer insulating jacket made of teflon or PVC.

Network Cabling
How Fiber Optics Work

Advantages:

• No cables needed
• Multiple channels available
• Wide bandwidth

Disadvantages:

• Line-of-sight will be disrupted if any obstacle, such as new buildings, are in the way
• Signal absorption by the atmosphere. Microwaves suffer from attenuation due to atmospheric conditions.
• Towers are expensive to build

Microwave Transmission

A satellite is any object that revolves around a planet in a circular or elliptical path.

Satellites have many purposes including data communications, scientific applications and weather analysis. Satellite transmission requires an unobstructed line of sight. The line of site will be between the orbiting satellite and a station on Earth. Satellite signals must travel in straight lines but do not have the limitations of ground based wireless transmission, such as the curvature of the Earth.

Microwave signals from a satellite can be transmitted to any place on Earth which means that high quality communications can be made available to remote areas of the world without requiring the massive investment in ground-based equipment.

Advantages:

• High bandwidth
• Coverage over a large geographical area
• Can be cheaper over long distances

Disadvantages:

• Huge initial cost
• Noise and interference
• Propagation delay

Satellite Transmission

Satellite Communication Exaplained

Infrared technology allows computing devices to communicate via short-range wireless signals. With infrared, computers can transfer files and other digital data bidirectionally. The infrared transmission technology used in computers is similar to that used in consumer product remote control units.

It has a relateively short range that also increases the security of data transfer. The Nintendo Wii controller uses infrared to transmit gestures and movement to the game console.

Infrared

Radio transmission works with or without line of sight. If line of sight is possible then transmission can take place between sending antenna and receiving antenna.

In large external networks such as mobile phone towers the placement of antennas has to take into account the curvature of the Earth with antenna being built taller accordingly. This will also allow for greater transmission distances. If line of sight cannot be implemented then signals can be broadcast to the upper layers or the atmosphere or space and then transmitted back to Earth.

Smaller radio transmissions such as WiFi or Bluetooth also use radio technology.

• What are the most common frequencies of the radio spectrum?
• Why do different frequencies have different purposes?

Radio Frequencies