IBM Aptiva - Frequently Asked Questions about V.90 and 56K Connections
Q. What is V.90?
A. An International Telecommunication Union (ITU) committee agreed to a draft standard for high-speed PCM (pulse code modulation) modems early in February 1998. This standard is called V.90 and is expected to be ratified late in 1998. V.90 is a protocol that allows two earlier PCM Protocols, K56Flex and x2, to interoperate with each other after they have been upgraded to V.90. Interoperability is a key factor that enables many different modem brands to connect. Like previous PCM protocols, V.90 is asymmetric. This means that your modem can receive data at a rate faster than that at which it sends data.
Q. Will I be able to connect at 56Kbps?
A. No. Public networks currently limit maximum download speeds to about 53Kbps. Actual connect speeds depend on many factors and are often less than the maximum possible. The following are some, but not all, of the many factors that could prevent a high speed V.90, K56flex, or x2 connection and result in a connect rate of 33.6Kbps or less. It is possible to have more than one condition present on your phone line.
1. Multiple Analog Loops: In order to get a high speed (over 33.6Kbps) V.90, K56flex, or x2 connection, you must have only one analog loop in the circuit between you and your Internet Service Provider (ISP). Digital Loop Carriers are devices that are frequently installed in neighborhoods that may impose restrictions on the modem's performance by adding a second analog loop between your modem and the phone company central office.
The phone line from your house is an analog line. Once the analog signal gets to the phone company central office, it is translated into a digital signal and sent out over the public network to your Internet Service Provider (ISP). Some signal data is lost in the translation - consequently, the more times the data is translated from analog to digital and back again, the worse the quality of the transmission. If there is more than one analog to digital conversion between you and the phone company central office, a high speed (over 33.6Kbps) connection may not be possible. The phone networks in older, heavily-populated areas utilize equipment that performs up to six analog to digital conversions.
2. Incompatible Protocol: Your ISP must have "head-end" equipment compatible with the protocol of your modem.
3. Phone Line Equipment: The primary purpose of the phone company's residential phone lines is to provide clear voice connections. Some equipment the phone company installs to make voice connections clearer actually can prevent high speed data connections. For example, your phone company may have installed a signal amplifier, loading coils, on the analog portion of your phone line. This equipment boosts Voice signal quality across longer distances, but causes some signal distortion and may inhibit your ability to achieve a high speed connection.
Frequently, in newer neighborhoods, Subscriber Line Interface Circuits (SLICs) and Universal Digital Loop Carriers (UDLCs) are used to multiplex many residential copper lines to a central point whereby the voice traffic is sent back to the central office digitally. It is not possible to achieve high speed modem connections when connected to a UDLC. A SLIC does have some impediments to high speed connections, but if call signaling is set up properly (one or more bits may be "stolen" for the purposes of call signaling), high speed connections may be possible. Your phone company can determine if you are connected to a SLIC or a Digital Loop Carrier. SLICs appear as a small green box in your neighborhood.
Some lines have installed a "pad" installed before getting to the phone company central office. The purpose of the pad is to equalize the volume on each end of a voice call. An analog pad introduces an additional conversion from analog to digital, and will prevent a high speed data connection.
Contact your phone company for further information on your phone line.
4. Long Distance Connection: A local access number does not necessarily mean a local call. Some ISP's use call forwarding to extend their geographical "reach". This may inhibit high speed data connections. Contact your ISP for further information.
5. Other Electrical Equipment: Line noise can be added by additional phone equipment installed on your phone line. Disconnect any Fax machines, surge suppressers, Caller ID boxes, etc. and try again. Noise may also be caused by environmental factors such as power lines.
Q. How do I upgrade my system to V.90?
A. If you recently purchased an Aptiva system with a K56Flex modem, an upgrade is available through Update Connector. To obtain the upgrade; double-click on the Update Connector desktop icon with the modem connected to the phone line and follow the instructions on the screen. As newer modem code becomes available, it is helpful to check Update Connector periodically.