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What is V.90?

V.90 is the official designator for the International Telecommunications Union's (ITU) draft recommendation for 56K modems. Known previously as V.pcm, the V.90 draft was approved in February 1998, clearing the way for universal compatibility among various 56K modems.

V.90 Technical Info

V.90 is a new technology that utilizes the telephone system in a way that has never been tried before. As a result, it has some requirements that were unnecessary in previous speed technologies. There are three primary requirements for V.90 speeds to be achieved:

  1. Digital at one end, the end where the V.90 server lies. The digital line servicing the V.90 server must be an ISDN PRI, ISDN BRI or a trunk-side T1. This item is taken care of by the ISP/Online Service.
  2. V.90 support at both ends. In order to achieve V.90 speeds, both ends of the connection must support V.90. In other words, you must have a V.90 modem (called a V.90 client) on your end and your ISP/Online Service must have a V.90 device on their end (called a V.90 server).
  3. One analog section. This is the section most relevant to you. In almost all residential homes, the phone line going into your modem or phone is analog, but that does not mean that it is all analog to the Central Office.

After determining that your line is capable of V.90 connections, there are other issues that can hamper V.90 connections, either by reducing the speed capable or reducing the number of times that you actually achieve a V.90 connection. Some of these issues are:

  • Load coils - these are primarily in long wire lengths to improve the quality of a voice call. They will not necessarily prevent V.90, but they can reduce the speed of your V.90 connections.
  • Pads - these come in primarily two forms: digital and analog. Both types are used to balance the volume between different lines, so that the volume of the voice call is the same on both ends within a reasonable range. With a digital pad, the digital data is manipulated to adjust the volume. This may cause a reduction in V.90 speeds, but it should not prevent V.90 connections. With analog pads, the digital data is converted to analog where the volume is adjusted and then converted back to digital. Because there is more than one analog section in such a path, it will prevent a V.90 connection.
  • Wiring - Wiring in the home or in the phone companies area can also hinder V.90 connections or speeds. Your V.90 speeds can be reduced if the lines that you are connected on are old and subject to interference.

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