Telecommunications technology transmits information by electromagnetic means over media such as telephone wires or radio waves. The information may be voice, facsimile, data, radio, or television signals. The electronic signals that are transmitted can be either analogue or digital. The advantages of digital transmission are high reliability and low cost. Digital switching systems are much cheaper than analogue systems.
In analogue modulation, the signals are transmitted directly (without converting them to digital form) by amplitude modulation or frequency modulation. For digital transmission the analogue signals must be converted to a digital form. Then the digitized signal is passed through a source encoder, which reduces redundant binary information. After source encoding, the digitized signal is processed in a channel encoder, which introduces redundant information that allows errors (degradation by noise or distortion) to be detected and corrected. The encoded signal is made suitable for transmission by modulation onto a carrier wave. When a signal reaches its destination, the device on the receiving end converts the electronic signal back into an understandable message – sound on a telephone, images on a television, or words and pictures on a computer.
There are three main methods of electromagnetic signal transmission: wire, radio and optical.
Telecommunications is the fastest growing segment of technology today. Telecommunications technologists are needed to plan, install and maintain state-of-the-art telephone systems, cable TV and computer networks. Although technologists have knowledge of theoretical topics, they tend to focus on salving practical design and application problems. Training covers a wide range of telecoms-related topics. Here is the content from one such course:
Part 1: Operating Systems
Part 2: Analogue Communications
Part 3: Telecommunications Fundamentals
Part 4: Telecommunications Fundamentals Lab
Part 5: Digital Electronics
Part 6: Telecommunications Networking
Part 7: Fundamentals of Optical Communications
Part 8: Data Communications Networking
A wide variety of information can be transferred through a telecommunications system, including voice and music, still-frame and full-motion pictures, computer files and applications, and telegraphic data.
The telephone is an instrument used for sending and receiving voice messages and data. Most phone calls involve two people, but the phone network can also be used to pay bills and retrieve messages from answering machines. Private individuals will usually have their own phone line; a large business will usually have its own switching machine, called a Private Branch Exchange (PBX), with many lines, all of which can be reached by dialing one number.
Radio transmission broadcasts signals that are intended for general public reception. With an omnidirectional antenna, radio signals are transmitted over a wide area. In a point-to-point radio channel, a directional transmitting antenna focuses the wave into a narrow beam, which is directed toward a single receiver. Broadcasts may be audible only, as in radio, or visual or a combination of both, as in television.
Two applications of telecoms are telephony and television.
A videophone is a personal video camera and display, a microphone and speaker, and a data-conversion device.
A cordless telephone is a device which plugs directly into an existing telephone jack, allowing limited mobility within the home, garden or office. Telephony has been revolutionized by cellular (cell or mobile) telephones, which are personal portable devices.
Facsimile, or fax, refers to the transmission of print: text, fixed images or drawings by wire or radio channels or undersea cable.