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Currently, a Plain Old Telephone Service (POTS) analog line represents a single open channel or pipe between two parties. Once a call is placed, that physical connection between the two parties can not be used by anyone else or for any other purpose. Thus, we see more people installing a second line for the teenagers, the fax, or home office.
ISDN is digital, and both voice and data are sent as digital packets. These packets, like cars on a freeway, can be caravaned with packets of other conversations traveling on the same circuit. Each packet contains calling information so that it will exit to the appropriate party. Since ISDN carries more calls over the existing infrastructure, you can see that it is in the best interest of the phone companies to convert to ISDN, and it could be in your best interest too!
ISDN is defined as two bearer channels (B-channels) and one signalling data channel (D-channel). That means that it will bear two phone calls at the same time. The signalling channel is used to set up the call and ring the other party. Since the signalling channel is not used much after the the call has been connected, there is also the option to send small amounts of data over the D-channel (a third call).
Compare B-channel transmission capabilities against an analog modem. A typical modem can achieve a 14,400 bit per second transfer, and 56,000 bps is cutting edge. The ISDN B-channel will support up to 64,000 bps, and if the two channels are used together, then double the speed to 128,000 bps. Tack on the D-channel’s 16,000 bps capability, and you could get a whopping 144,000 bps. That’s 10 times, or 1000%, faster than a typical modem. That’s video quality.
Use those channels independently and you can have two voice conversations, or two data calls, or one voice and one data call, all occurring simultaneously and to different destinations. With D-channel packets, you can have a third call handling small data transfers such as customer credit card validation.
Digital ISDN means your equipment must also be digital. Analog equipment such as fax, modem, and your POTS telephone will not work directly on your new ISDN line. In addition, ISDN is not powered like your analog phone, so you must either keep one analog line for power-outage emergencies or else use a battery backed NT1 on one of your ISDN lines.
You can obtain special battery-backed extended NT1s that pass one ISDN B-channel through and convert the other B-channel to an analog port, so that you may utilize a single ISDN line for all your needs. But most users add ISDN as a second line. With this arrangement, you can have one high-speed line for digital data and voice, and keep the other for fax, modem, and analog voice communications.
1. ISDN provides significantly greater speed for data transmission. If you currently transfer files by modem, then ISDN can greatly increase your efficiency. If you are browsing the Internet, you may already have reached the tolerable limit of your analog modem and will be elated with ISDN service.
2. ISDN provides crystal clear digital voice. Even if the other party is still on an analog line, you will hear a clearer call.
3. A single ISDN line supports two phone calls (and two phone numbers) and a third data link.
4. ISDN call control features are on par with corporate telephone switchboard features. You can order call Hold, Transfer, Conference, Caller ID, special ringing, and an assortment of other calling features.
5. ISDN is an affordable alternative to leased lines. If you have considered leased lines in order to get faster data rates, but were deterred by the pricing, consider ISDN. The only question is whether you need a continuous connection or a periodic dial-up service. For high volume continuous connections, leased lines may still be the best solution for you, but compare the cost of ISDN lines and services before you make any decisions.
For dial-up services, ISDN is the hands-down winner over both leased lines and analog solutions. Consider the following implementations of ISDN:
In the medical profession, quick response time is essential. A number of medical facilities are implementing ISDN in order to transfer images and data at high speeds. Images such as X-rays can be transferred to a specialist at another facility or at home for review. These types of transfers do not require continuous connectivity.
The transfer of any graphic image requires bandwidth if it is going to be sent efficiently. Many graphic artists work hours perfecting their work only to spend hours on an analog modem trying to transfer it to a client or central site. An ISDN solution solves this problem by decreasing the amount of connect time, which saves money, releases the computer quickly, and improves productivity.
In many areas, telecommuting is quickly becoming a requirement instead of a luxury. EPA rulings in several cities require that a certain percentage of the workforce work from home on days when the air quality is deemed poor. ISDN can be the best all-around solution for moving a portion of the workforce into the home. Just one ISDN line can provide a simultaneous voice and data connection for the worker, and just one billing per home for the accounting department!
An ISDN connection to the Internet means faster Net Surfing! See the ISDN to Internet section devoted to this topic.
Your ISDN line will support up to eight different digital devices, and each one can have a different telephone number. With two B-channels, any two at a time can be active on calls. That's a lot of flexibility, a lot of teenagers, or a lot of computer equipment.
ISDN availability is sweeping throughout the U.S. If you are unsure about the availability or cost of ISDN, check with your local telephone company for details.