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Mass-market telephony
A major development starting in 2004 has been the introduction
of mass-market VoIP services over broadband Internet access
services, in which subscribers make and receive calls as they
would over the PSTN. This requires an analog telephone adapter
(ATA) to connect a telephone to the broadband Internet connection.
Full phone service VoIP phone companies provide inbound and
outbound calling with Direct Inbound Dialing. Many offer unlimited
calling to the U.S., and sometimes to Canada or to selected
countries in Europe or Asia, for a flat monthly fee. One advantage
of this is the ability to make and receive calls as one would
at home, anywhere in the world, at no extra cost. As calls go
via IP, this does not incur charges as call diversion does via
the PSTN, and the called party does not have to pay for the
call.
For example, somebody may call someone on a number with a U.S.
area code, but one could be in London, and if someone were to
call another number with that area code, it would be treated
as a local call, regardless of where that person is in the world.
However, the broadband phone is likely to complement, rather
than replace a PSTN line, as it still needs a power supply,
while calling the U.S. emergency services number 911, may not
automatically be routed to the nearest local emergency dispatch
center, and would be of no use for subscribers outside the U.S.
Another challenge for these services is the proper handling
of outgoing calls from fax machines, TiVo/ReplayTV boxes, satellite
television receivers, alarm systems, conventional modems or
FAXmodems, and other similar devices that depend on access to
a voice-grade telephone line for some or all of their functionality.
At present, these types of calls sometimes go through without
any problems, but in other cases they will not go through at
all. And in some cases, this equipment can be made to work over
a VoIP connection if the sending speed can be changed to a lower
bits per second rate. If VoIP and cellular substitution becomes
very popular, some ancillary equipment makers may be forced
to redesign equipment, because it would no longer be possible
to assume a conventional voice-grade telephone line would be
available in almost all homes in North America and Western-Europe.
The TestYourVoIP website offers a free service to test the quality
of or diagnose an Internet connection by placing simulated VoIP
calls from any Java-enabled Web browser, or from any phone or
VoIP device capable of calling the PSTN network.
Corporate and telco use
Although few office environments and even fewer homes use a
pure VoIP infrastructure, telecommunications providers routinely
use IP telephony, often over a dedicated IP network, to connect
switching stations, converting voice signals to IP packets and
back. The result is a data-abstracted digital network which
the provider can easily upgrade and use for multiple purposes.
Corporate customer telephone support often use IP telephony
exclusively to take advantage of the data abstraction. The benefit
of using this technology is the need for only one class of circuit
connection and better bandwidth use. Companies can acquire their
own gateways to eliminate third-party costs, which is worthwhile
in some situations.
VoIP is widely employed by carriers, especially for international
telephone calls. It is commonly used to route traffic starting
and ending at conventional PSTN telephones.
Many telecommunications companies are looking at the IP Multimedia
Subsystem (IMS) which will merge Internet technologies with
the mobile world, using a pure VoIP infrastructure. It will
enable them to upgrade their existing systems while embracing
Internet technologies such as the Web, email, instant messaging,
presence, and video conferencing. It will also allow existing
VoIP systems to interface with the conventional PSTN and mobile
phones.
Electronic Numbering (Enum) uses standard phone numbers (E.164),
but allows connections entirely over the Internet. If the other
party uses Enum, the only expense is the Internet connection.
Use in Amateur Radio
Amateur radio has adopted VoIP by linking repeaters and users
with Echolink, IRLP, Dstar and EQSO. Echolink and IRLP are programs/systems
based upon the Speak Freely VoIP open source software. In fact,
Echolink allows users to connect to repeaters via their computer
(over the internet) rather than by using a radio. By using VoIP
Amateur Radio operators are able to create large repeater networks
with repeaters all over the world where operators can access
the system with actual ham radios.
Ham Radio operators using radios are able to tune to repeaters
with VoIP capabilities and use DTMF buttons to command the repeater
to connect to various other repeaters, thus allowing them to
talk to people all around the world, however powerful their
radio.
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