VoIP is often used abstractly to refer to the actual transmission of
voice (rather than the protocol implementing it). This latter concept is also
referred to as IP telephony, Internet telephony, voice over broadband, broadband
telephony, and broadband phone. The last two are arguably incorrect because
telephone-quality voice communications are, by definition, narrowband.
VoIP providers may be viewed as commercial realizations of the experimental
Network Voice Protocol (1973) invented for the ARPANET providers. Some cost
savings are due to utilizing a single network to carry voice and data,
especially where users have underused network capacity that can carry VoIP at no
additional cost. VoIP to VoIP phone calls are sometimes free, while VoIP calls
connecting to public switched telephone networks (VoIP-to-PSTN), may have a cost
that is borne by the VoIP user.
One advantage of these two types of services is the
ability to make and receive calls as one would at home, anywhere in the world,
at no extra cost. No additional charges are incurred, as call diversion via the
PSTN would, and the called party does not have to pay for the call. For example,
if a subscriber with a home phone number in the U.S. or Canada calls someone
else within his local calling area, it will be treated as a local call
regardless of where that person is in the world. Often the user may elect to use
someone else's area code as his own to minimize phone costs to a frequently
called long-distance number.
For some users, the broadband phone complements, rather than replaces, a PSTN
line, due to a number of inconveniences compared to traditional services. VoIP
requires a broadband Internet connection and, if a telephone adapter is used, a
power adapter is usually needed. In the case of a power failure, VoIP services
will generally not function. Additionally, a call to an emergency services
number may not automatically be routed to the nearest local emergency dispatch
center. Some VoIP providers only handle emergency call for one country. Some
VoIP providers offer users the ability to register their address so that
emergency services work as expected.
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Sound , TalkSwitch ,
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Warner Brothers,
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