Closed-circuit radio
Encyclopedia
A closed-circuit radio is a radio
that emits over a very small range, typically a college campus. This system can be achieved from two ways:
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
that emits over a very small range, typically a college campus. This system can be achieved from two ways:
- By tying into the PA SystemPublic addressA public address system is an electronic amplification system with a mixer, amplifier and loudspeakers, used to reinforce a sound source, e.g., a person giving a speech, a DJ playing prerecorded music, and distributing the sound throughout a venue or building.Simple PA systems are often used in...
- By using existing power linesElectric power transmissionElectric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...
, telephones lines, pipes, etc. to transmit a carrier currentCarrier currentCarrier current is a method of low power AM radio transmission that uses the AC electrical system of a building to propagate a medium frequency, AM signal to a relatively small area, such as a building or a group of buildings...