Media of CommunicationRadio and Sound Recording Cai Bingxin 20129869
Radio• Radio is the transmission of signals through free space by electromagnetic waves with frequencies significantly below visible light, in the radio frequency range, from about 3 kHz to 300 GHz. These waves are called radio waves. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space.• Information, such as sound, is carried by systematically changing (modulating) some property of the radiated waves, such as their amplitude, frequency, phase, or pulse width. When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form.
Radio communication system• A radio communication system sends signals by radio. Types of radio communication systems deployed depend on technology, standards, regulations, radio spectrum allocation, user requirements, service positioning, and investment.• The radio equipment involved in communication systems includes a transmitter and a receiver, each having an antenna and appropriate terminal equipment such as a microphone at the transmitter and a loudspeaker at the receiver in the case of a voice-communication system.• The power consumed in a transmitting station varies depending on the distance of communication and the transmission conditions. The power received at the receiving station is usually only a tiny fraction of the transmitters output, since communication depends on receiving the information, not the energy, that was transmitted.
EXAMPLE----• The BBC is a semi-autonomous public service broadcaster that operates under a Royal Charter and a Licence and Agreement from the Home Secretary. Within the United Kingdom its work is funded principally by an annual television licence fee, which is charged to all British households, companies and organisations using any type of equipment to record and/or receive live television broadcasts; the level of the fee is set annually by the British Government and agreed by Parliament.• Outside the UK, the BBC World Service has provided services by direct broadcasting and re-transmission contracts by sound radio since the inauguration of the BBC Empire Service in December 1932, and more recently by television and online. Though sharing some of the facilities of the domestic services, particularly for news and current affairs output, the World Service has a separate Managing Director, and its operating costs have historically been funded mainly by direct grants from the British government. These grants were determined independently of the domestic licence fee and were usually awarded from the budget of the Foreign and Commonwealth Office.
Sound Recording• Sound recording and reproduction is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording. Acoustic analog recording is achieved by a small microphone diaphragm that can detect changes in atmospheric pressure (acoustic sound waves) and record them as a graphic representation of the sound waves on a medium such as a phonograph (in which a stylus senses grooves on a record).
EXAMPLE—Black Box• A flight data recorder (FDR) also called black box is a placeholder name used casually to refer to a collection of several different recording devices used in transportation: the flight recorders (cockpit voice recorder) in aircraft, the event recorder in railway locomotives, the event data recorder in automobiles, message case in ships, and other recording devices in various vehicles.