Types of communication links

There are several types of communication links. Some of them may be already known.
pairs
One of the most common means of communication is a pair of wires, also known as cable. pairs of wires are twisted together in the cable, which is then insulated. pairs of wires are inexpensive. Moreover, they are often used because it is already installed in the building for other purposes or because they are already used in telephone systems. However, they are prone to electrical interference and noise. Noise is something that causes distortions in the signal after it is received. High-voltage equipment, and even the sun can be a source of noise.
Coaxial cables
Known for sending a strong signal, coaxial cable is a shielded cable in the housing. Harness can be laid underground or underwater. These cables can transmit data much faster than the wire pairs and are less prone to interference. These types of cables that carry cable TV in their homes. cable companies are now coming out of Internet services to homes (Cox @ Home is an example of Rhode Island), which use cable lines and providing access much faster than telephone lines can provide.
Fiber Optics
Traditionally, most telephone lines of the data transmitted by electrical wires made of metal, usually copper. These metal wires need to be protected from water and other corrosive substances. Fiber optic technology eliminates this requirement. Instead of using electricity to transmit data, fiber optics uses light. Cables are made of glass fibers, each thinner than a human hair that can direct the beam of light for miles. Fiber-optic cables transmit data faster than some technologies, but the materials are much lighter and cheaper than metal cables. You can also send and receive a wider range of frequencies at one time. The frequency range that the device can support is known as its bandwidth, bandwidth is a measure of the link. Broad band optical fiber translates into promising opportunities in multimedia, since fiber is well suited to handle all types of data, voice, images, music and video at the same time.
Microwave Transmission
Another popular medium, microwave transmission, which uses the so-called line-of-sight transmission of data signals through the atmosphere. Since these signals can not bend around the curvature of the earth, relay stations, antennas are often high, for example, on the tops of mountains and buildings, are positioned at about 30 kilometers to continue broadcasting. microwave transmission has the speed, efficiency and ease of implementation. Unfortunately, in the main cities and tall buildings may interfere with microwave transmission.
Satellite Broadcast
The basic elements of satellite transmission are the ground stations that send and receive signals and the satellite component of the transponder. The transponder receives a signal from earth station, amplifies the signal, frequency and retransmits the data to ground receiving station. (The frequency is changed so that the weaker signals will not be limited by the strong outgoing signals.) This whole process takes a matter of seconds.
If the signal must travel thousands of kilometers, the satellites are usually part of the link. Messages sent around the world is likely to travel by cable or other physical link only to the nearest earth station satellite transmission. From there it is transmitted to the satellite, which sends him back to earth to another transmission station near the place of destination data. satellite communications in space, where they are suspended at 22,300 miles above the earth. Why 22,300 miles? It is there to reach geosynchronous orbit satellites in orbit, which allows them to stay put in the same spot on earth.
Mixing and matching
Network system is not limited to one type of link and, in fact, often working in different combinations, especially over long distances. Office worker who needs data from the PC's on the opposite bank is likely to pair wires used in telephone line, and then microwave and satellite transmission. Amazingly, the journey across the country and back, along with a brief stop to raise the data may take only a few seconds.