TYPE OF TRANSMISSION MEDIA

TYPE OF WIRED

1. Twisted Pair Cable

A transmission medium consisting of pairs of twisted copper wires arranged in a regular spiral pattern to minimize the electromagnetic interference between adjacent pairs. Low frequency transmission medium only can transmit 1 Mbps over short distances. They are mainly used to transmit analog signals but they can be used for digital signals.

2. Coaxial Cable

Coaxial cable consists of a core made of solid copper surrounded by insulation a braided metal shielding and an outer cover. A transmission medium consisting of thickly insulated copper wire which can transmit a large volume of data than twisted wire.

3. Fiber-optic Cable

New transmission medium used by telephone companies in place of long-distance trunk lines. This cable also used by private companies in implementing local data communication networks. Optical fiber consists of a glass cladding with slightly lower refractive index. Fiber optic cable is used as the high speed backbone.



TYPE OF WIRELESS

·                     Infrared is a wireless transmission medium that sends signals using infrared light waves. Infrared is used in devices such as the mouse, wireless keyboard and printers. Some manufacturers provide a special port called the IrDA port that allows a wireless keyboard to communicate with a PC. Infrared signals have frequencies between 300 GHz to 400 THz.

·                     Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. When an antenna transmits radio waves, they are propagated in all directions. This means that the sending and receiving antennas do not have to be aligned. Our AM and FM radio stations, cordless phones and televisions are examples of multicasting.

·                     Satellite is an object which has been placed into orbit by human endeavor. A communication satellite is a space station that receives microwave signals from an earth-based station, amplifies (strengthen) the signals, and broadcasts the signals back over a wide area to any number of earth-based stations.