Telecommunication
The other meaning of the term "channel" in telecommunications is seen in the phrase communications channel, which is a subdivision of a transmission medium so that it can be used to send multiple streams of information simultaneously. For example, one radio station can broadcast radio waves into free space at frequencies in the neighborhood of 94.5 MHz (megahertz) while another radio station can simultaneously broadcast radio waves at frequencies in the neighborhood of 96.1 MHz. Each radio station would transmit radio waves over a frequency bandwidth of about 180 kHz (kilohertz), centered at frequencies such as the above, which are called the "carrier frequencies". Each station in this example is separated from its adjacent stations by 200 kHz, and the difference between 200 kHz and 180 kHz (20 kHz) is an engineering allowance for the imperfections in the communication system.
Radio Feltham
In November 2004, Radio Feltham celebrated its 10-year broadcasting milestone by switching its transmitters from 999AM to 87.8FM. The station, run by young prisoners aged 15 to 21, expanded its usual in-house broadcast to offer a community service of music, news and information to Feltham, to a potential audience of one million residents within a 10 mile radius of HMP Feltham.