International Phone Card Review
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What Else Is Necessary
Using the Internet, it is possible to exchange digital information. The most known example is an e-mail. Moreover, it is technically
possible to digitize and send sound as well. And in this sense, IP-telephony systems use the Internet for sending a fax or a voice
between two users of computers in real time.
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We can estimate connection quality using the following basic descriptions:
On the first two characteristics, connection quality was considerably multiplied by comparison to the first versions of IP-telephony
systems which assumed distortion and breaking of speech.
- Level of distortion of a voice
- Frequency of disappearing a vocal package
- Delay length (between pronouncing of a phrase by the first user and moment when it will be heard by the second user).
The improvement of voice encoding and renewal of the lost packages
attaining a level when users understand speech easily enough. The delays influence on the rate of conversation. It is known that the
delay to 250 milliseconds is practically unnoticeable for a human. The IP-telephony solutions existing for today exceed this limit.
Thus, a talk looks like one with an ordinary public-call network through a satellite. Even in such quality, connections through
IP-telephony fully befit for many appendixes, including phone calls for international and domestic destinations with prepaid calling
Except for it, the delays diminish due to the following factors:
Although updating routers needs some time, the world of the Internet moves very quickly and in a correct direction.
- Public-call servers are perfected (their developers contest with the delays, improving the work algorithms).
- Private (corporate) networks are developing (their proprietors can control the width of key-in bar and sizes of delay).
- The Internet is developing. Together with the Internet service providers, the Internet Engineering Task Force (IETF) offers new
technologies such as Reservation Protocol (RSVP), which allow reserving the key-in bar.
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