The other 56K modem technology is X2, developed by 3Com/US Robotics. The two technologies are not compatible with one another. If you have a modem which is X2 compatible, you will be able to use it to connect at normal modem speeds, but because K56Flex and X2 are not compatible, you won't be able to take advantage of increased download speeds.

If you are using a modem that fully supports the v.90 standard it will default to that standard when connecting into our access server allowing you to use the maximum speed your telephone lines can handle.

What is the v.90 standard you ask?  Basically it's a modem standard that was derived to bridge the gap between the two other 56k standards that evolved and were not compatible with each other (the above mentioned X2 and Kflex standards).  It allows modems from different manufacturers to connect at the highest possible speed.

1. How does it work?
2. What kind of modem do I need?
3. What kind of speed can I expect to achieve?

56K modems allow for a higher download speed than was previously possible with an analog modem. They do so by taking advantage of the nature of the connection between a dial-up client using an analog modem (presumably, you are one of those) and Full Radius, which has a digital connection to the Bell Atlantic central office. A Central Office, or CO, is the location of the telephone switches and other telco equipment for a given town or area.

When you send data from your analog device, the data is converted at the central office from an analog signal to a digital signal. This conversion from analog to digital introduces the most significant amount of noise to the communication, consequently slowing the communication down. However, this type of conversion is not necessary when data goes in the other direction because Full Radius has a digital connection to the public telephone network. This means that the communication will remain digital up until your central office, and at no point does it require a conversion from an analog to a digital signal. Both Kflex and v.90 technology take advantage of this to allow you greater download speeds via data compression.

In order to take advantage of Full Radius' upgrade to Kflex/v.90, you will need to ensure that your modem supports either the v.90 or Kflex  technology. You can find out whether or not it does by contacting the modem manufacturer.

If you are planning to purchase a new modem, SHOP CAREFULLY. You will want to ensure via careful label-reading that the product you are purchasing actually supports Kflex or v.90 rather than being upgradable to either standard.  If you are going to purchase a modem which is upgradable to either standard, you will want to make sure that it is a software, not a hardware upgrade. Another important feature to look for is whether or not the modem you are purchasing is a Winmodem or a regular modem.  It has been our experience that Winmodems do not perform anywhere near as well as a standard modem.  To be on the safe side, you should also be certain that you can return your new modem.

We at Full Radius have tested the following modems and can ensure compatibility with our system:  3Com/US Robotics 56k V.Everything with v.90 upgrade, 3Com/US Robotics v.90 Data/Fax, 3Com/US Robotics Sportster 56k and Zoom Telephonics Dual-mode 56k v.90 modem.  We are constantly updating our list of supported modems so please check back often.

While you will probably not be able to achieve a true 56K connection with any brand of  Kflex or v.90 analog modem, you will probably get a faster connection than you would with a 28.8 or a 33.6 modem. (Remember that those are also optimum speeds.) Line noise and the distance your communication will travel are two factors that can influence the speed you are able to achieve with a 56K modem. The download speeds you will be able to achieve will probably range between 32 and 48 kbps.

56K analog technology is asymmetrical, in other words, it allows different transmission speeds depending on whether you are uploading or downloading. Your upload speeds are going to be limited to 28.8 or 33.6 depending on your modem while your download speeds could peek to 53k.

One more thing to keep in mind is that not all phone wiring can support higher speed modems.  The telephone company is still only supporting data speeds up to 21,600.   One way to find out if your wiring can support the higher speeds is to use 3Com/US Robotics automated line tester.  You can find it at http://www.3com.com/56k/need4_56k/linetest.html.