Radio
In radio, remotes are often used for special events, such as concerts or sporting events, where either the entire event or advertisements for the event are broadcast on location. The cost of personnel and equipment is usually paid for by the host at each performance. However, if the event is recurring, such as a weekly broadcast from a nightclub, then dedicated lines are usually installed by the local telephone company in order to save on costs. Originally, analog audio broadcasts were sent through telephone hybrids, which, although low quality, were found to be acceptable for voice broadcasts. Later, frequency extenders were developed that used additional lines, shifting higher treble audio frequencies down on one end and back up on the other, providing a reasonable reproduction of the original sound. Currently, digital lines, such as ISDN or DSL, are used to send compressed digital audio back to the studio. In addition, modern remote pickup units have become extremely portable and can transmit single-channel monophonic FM-quality audio over regular telephone lines using build-in modems and advanced compression algorithms (MPEG-4, etc.).
