Telecommunication How It works What It is Telecommunication

Telecommunication How It works

What It is? Telecommunication, devices and systems that transmit electronic or optical signals across long distances. such as a telephone system. n enables people to send and receive personal messages. n key medium for delivering news, data, information, and entertainment. n

Way of sending Message Point-to-point : One sender to a single receiver such as telephone conversation; n Point-to multi point : one sender to many receiver such as television, It often called Broadcast; n

How the signals sent? n n n Telecommunications devices convert different types of information, such as sound and video, into electronic or optical signals. Electronic signals travel along a medium such as copper wire or are carried over the air as radio waves. Optical signals travel along optical fiber cable; the device on the receiving end converts the signal back into an understandable message, such as words and pictures on a computer screen.

Types of signal n n n Analog signal Digital signal Optical signal n analog or digital refers to the method used to convert information into an electrical signal

Analog signal n n An analog signal is any continuously variable signal in an analog sound recording, the variation in pressure of a sound striking a microphone creates a corresponding variation in the current passing through it. An increase in the volume of the sound causes the fluctuation of the current to increase

Digital signal 0 volt means 0 n 5 volts means 1 n

Optical signal Pulse beam of laser light n LED (Light Emitting Diode) send signal n Fiber optic receiver Receive fiber optic signals n

Transmission medium l Cable l Fiber-optic l Micro-wave l Satellite

Coaxial cable Developed in 1936 l Made of copper wire l Expensive l

Fiber Optics l Message are digitally coded into pulses of light l TAT 9 fiber optic cable can carry more than 75, 000 telephone conversation at a time

Microwave relay Relay from station to station l Needs a clear line of sight between sending and receiving station l Average distance between stations 40 km l As many as 600 telephone conversations can be transmitted over one microwave relay channel. l

Satellite communication l l l Started at 1969 with series of satellites Orbit 35, 880 km above the earth Powered by solar energy Use micro wave for transmission can relay up to 33, 000 calls simultaneously as well as several television channels.

Way of transmission o Simplex: One way communication o Half Duplex: communications in both directions, but only one direction at a time o Duplex: communication in both directions simultaneously

Applications Telegraph Fax Telephone Radio Television Global Positioning System Voice Over IP

Computer network

Telephone & cellular Communication

Global Positioning System § space-based radionavigation system consisting of 24 satellites and ground support. § accurate information about their position, time, anywhere in the world and in all weather conditions.

How GPS Works § GPS satellites fly in circular orbits at an altitude of 20, 100 km (12, 500 mi) and with a period of 12 hours § point their solar panels toward the sun and their antennas toward the earth § Send the signals to the receiver § From that signal receiver calculate its position on earth

Application of GPS § Military equipment such as fighters, bombers, tankers, helicopters, ships, submarines, tanks, jeeps, and soldiers § Airplane and ships use it for route navigation § used to route and monitor delivery vans and emergency vehicles § car navigation system § Because the GPS user does not need to communicate with the satellite, GPS can serve an unlimited number of users.

Inventor In 1837 Samuel Morse invented the first workable telegraph l Alexander Graham Bell invented telephone in 1876 l Marconi invented Radio in 1895 l