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| Main » 2012 » June » 7 » free calls from pc to phone
12:15 PM free calls from pc to phone |
The technology that enables phone
calls from a PC is called IP Telephony
or Voice over Internet Protocol (VoIP)
. It is a booming industry catered to
by a range of companies, some
charging a subscription, others
making the technology available free
of charge.
Technology
*
The technological foundation
for VoIP was originally only available
for private companies. The network
speeds required for an interactive
conversation couldn't be achieved
over the Internet, but private
networks provided sufficient data
throughput for their limited areas.
The introduction of Broadband
Internet made adequate speeds
available to the general public and
VoIP became a viable industry.
Requirements
*
In order to connect a phone
call through a PC, a user needs a
Broadband Internet connection with a
minimum throughput of 30kbps
(kilobits per second) both uploading
and downloading. If several phone
lines are channelled over the same
Internet connection, the amount of
bandwidth required increases
proportionately. A high quality call
needs at least 60kbps of upload and
download speed. The PC also needs
to have a speaker and a microphone
integrated into it, or attached to it.
With this equipment, VoIP software
installed on the PC can give the user
phone call capabilities.
Service Formats
*
VoIP services based on a PC
are closely related to Internet
Messenger/Chat systems. Most
Messenger systems, like MSN
Messenger, also include the capability
to communicate with speech. These
systems do not substitute for phone
calls, however, because they do not
allow the user to dial a telephone
number, and only other members of
the same chat system can be
contacted. More sophisticated
services like Skype enable the user
to dial telephone numbers and reach
telephones outside the membership
network.
Quality of Service
One of the biggest factors in
VoIP quality of service is the the
quality of sound reproduction. This is
influenced by the quality of
equipment the PC has for sound
recording and playback (the
microphone and speaker). A higher
sample rate from the VoIP software
will bring better quality sound. The
distance a call travels will affect the
sound quality. Delay produces echo,
and lost packets cause gaps in the
conversation. VoIP does not have
enough time to resend lost packets
and still make the delivery seem
instantaneous. This is why the sample
size of the software converting
speech into a digital signal is
important. More regular sampling
creates smaller data packets. The loss
of a small data packet will produce
fewer gaps than if a large one is lost.
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Views: 260 |
Added by: javed
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