Until the 1990s, broadcasting was mainly a matter of transferring
sound or video streams through the airwaves (or in some
developed countries, through cable as well) by means of
analogue signals. This was a linear process, with each element in
the content stream taking its turn to transmit behind the one that
went before it. This worked well enough, except for one thing: it
required a lot of bandwidth, i.e. a lot of capacity was taken up on
wireless electronic frequencies in order to carry signals in this
manner. The knock-on effect of this was that in the realm of the
airwaves, this meant that only a limited number of stations could
be accommodated on the radio spectrum. A radio frequency like
FM 105.7 would, for instance, be available for use by a single
analogue radio station. Other frequencies were often unsuitable
for audio transmission, or were better used for TV or cellular
telephony, or were reserved for military communications. In TV,
which uses UHF and VHF frequencies, it was the same story: one
station, one frequency. With limited frequencies, the effect was a
limit to the number of stations.

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