Integrated Services Digital Network (ISDN) is an older digital method of connection to networks or the internet. It uses the same copper wire coming into a home or business as an ordinary analogue phone line. A very large percentage of the phone lines in the country are capable of supporting ISDN. The major limitation is distance from the exchange and line splitters are also a problem.
How does it work?
ISDN offers two 'lines' over a single pair of copper. Each line is a 64kbps connection in each direction and both can be used together to achieve 128kbps but in this case, one pays for both connections. As it is a digital connection, the connection is established almost instantly so there is no annoying wait and screaming modem noises. To use a phone on ISDN, an analogue adapter is installed as part of the service because an ordinary home telephone is analogue and needs to be converted to a digital signal.
What does it cost?
Onetime costs:
It requires moderate expenditure as there is a connection fee and equipment is required. An existing phone line can be converted or a new one configured for ISDN can be ordered. The monthly line rental for an ISDN line is less than that of two analogue lines.
Ongoing costs:
There are several options available. The most basic is to set up a 'free' account and pay for the phone call costs. This works out to be very expensive if you are more than an occasional user. With the advent of flat rate dialup access, you can sign up with a provider to pay a flat monthly fee for a set number of hours access. There are several options available.
Advantages:
1. Relatively inexpensive to set up if you already have a phone line.
2. It is available to a large percentage of the population.
3. It is slightly faster than an analogue dialup connection (64kbps v. 48kbps) for the same dialup cost.
4. No waiting as 'dialup' is instantaneous.
Disadvantages:
1. Depending on your plan, it can be very expensive to use. During peak times in Ireland (from 8am to 6pm Monday to Friday) it costs approximately 5c per minute to connect or double that if both lines are used to achieve 128kbps. However, it is possible to sign up for flat rate access which provides for a flat monthly fee based on a set number of hours.
2. In the grand scheme of things, it is still slow to use although faster than analogue dialup.
3. Depending on the provider, you may get a busy signal at peak times during the day as all the modems at the providers side are in use.
4. While most PC's and Laptops now come with analogue modems built in, very few come with ISDN modems. It is an extra piece of equipment to purchase and maintain.
5. If using a portable device, this method of connection is not available widely but one can default to an analogue dialup relatively easily.
6. The service isn't available everywhere even if a line is present.