Can a Fax Machine Work on a DSL Connection?

Digital subscriber line (DSL) is an excellent low-cost way to share a single phone line between voice conversations and a high-speed data connection to the Internet. Because the nature of line sharing is a somewhat complex issue, however, some people have questions about exactly which services can be used on a line shared with DSL. This article will explain some of the basics about sharing DSL with other types of connections as well as explore some misconceptions and considerations about this arrangement.

Function

DSL is a high-speed data offering pioneered by and offered through telephone companies. These companies have a rich history in building and providing facilities to provide voice communications, and their DSL service rides the existing cables and wires into a customer's premises. Because DSL is an "always on" connection with no way to turn it off, service providers dedicated the uppermost frequencies capable of being carried on standard copper wires to the data connection; with a special DSL filter designed to separate these frequencies from standard voice communications, DSL remains completely separate from all other conversations on the telephone line.

Types

While DSL is a dedicated high-speed data connection, many other types of conversations can share its access line. The most common of these conversations is voice or a standard telephone call between two or more parties in which the callers talk with one another. Aside from voice, however, other "conversations" that may share the same line with DSL are fax calls, security system outbound reporting, satellite TV console conversations with the satellite TV service provider and even dial-up modem connections.

Identification

With DSL filters properly installed, digital subscriber line service can be very difficult to identify on a telephone line. If a telephone is plugged into a DSL line without being connected through a filter, or if a filter is faulty, the telephone user may hear a faint, constant, slightly wavering sound that is very similar to static. This "static" sound is actually computer data, modulated into sound, being passed across the telephone line between the modem and the DSL server. If such a sound exists on a telephone intended for voice or other non-DSL conversations, a DSL filter should be applied to the telephone jack being used.

Misconceptions

Some people believe that voice conversations have reduced clarity and that data connections are not possible when sharing a telephone line with DSL. The digital subscriber line service, however, overlaps only into an extremely small portion of the audible telephone frequency range; the vast majority of DSL data is passed at frequencies that can not be heard by humans but that can be carried by copper wires, meaning that voice calls on DSL lines retain the same crisp quality as if DSL were not present. In addition, fax machines and other data products modulate their data into sound that can be passed across the audible spectrum of telephone frequencies; these data conversations are entirely separate from--and not affected by--DSL.

Considerations

Although fax machines and other data connections can successfully share a telephone line with DSL service, care should be taken to ensure these machines are plugged into a functional DSL filter. If the DSL filter serving the fax machine or other data product should fail, the "static" sound produced by DSL service may spill over into the audible range, creating a "line noise" condition that can be fatal to data connections. Although DSL filters are of simple construction and rarely fail, experts recommend replacing filters on a routine basis, generally every 6 to 12 months.