Unlike analog telephone service, ISDN service is not yet
available everywhere. Your telephone company must have installed
the necessary equipment in the central office that serves
Because ISDN is a digital service, it is very sensitive to
outside interference. You must be within a given distance
of the telephone company equipment that serves you (typically
18,000 feet). Further, there can not be any other anomalies
near the wiring that might interfere with the transmission.
As a result, even if the equipment is installed at the central
office, it is possible you will not be able to get ISDN due
to line interference or your distance from the central office.
To determine whether your particular wiring will support ISDN,
the telephone company will perform what is known as a line
Some telephone companies offer what is called "ISDN
Anywhere", which means if you order ISDN, they will find
a way to get it to you. In cases where the telephone company
does not have the right equipment in the local central office
that serves you, they can use "line extension" technology
to serve you from another exchange. The use of line extension
technology may significantly increase the cost of your ISDN
Generally, ISDN has better availability in urban and suburban
areas, and is harder to get in rural areas.
To check if we has ISDN access in your area, check our dial-up
access list and check the ISDN column.