
Students Guide to Information
Technology
available capacity of
the
line. Modern packet switching, based upon
digital communications equipment, allows
a
number of calls to share
the same line. In addition, optic fibres allow broadband com-
munications (i.e. signals with a very broad bandwidth), and so can
carry a very large number of simultaneous telephone calls, as well as
TV signals.
Carrier waves and modulation
Most radio and telephone communications are based on the analogue
microphone/loudspeaker technology outlined in Chapter 5, and it is
therefore important that you understand the principles behind this.
Sound waves are converted to electrica ...