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Dial-up -- ISDN -- T1's

ISDN FAQ's

What is it?

Is it complicated?

Can I really get 128kbps Internet access?

But aren't there 56kbps analog modems available now, which I can use on my regular phone line?

Is ISDN expensive?

Are there other benefits?

What is it?

ISDN is a digital replacement for the current analog "POTS" telephone network. Like a regular phone you dial a phone number to get connected, and you can dial and talk to both ISDN and regular telephone numbers. But unlike a regular phone the line is fully digital, and as well as carrying crystal clear voice communications it can also carry 64kbps data communications. Better still, when you order ISDN service you actually get two lines (known as "B-channels") as a standard part of the package, and these lines can be conveniently combined together to connect you to the Internet at 128kbps.

Is it complicated?

ISDN does have some terminology to learn, and takes a few steps to set up, but it is as easy to use as the regular phone system when it is up and running.

When you order an ISDN line you get a "Basic Rate ISDN" (BRI) service. This breaks the line up into two B-channels and one D-channel. The two B-channels act like two separate phone lines and each has its own phone number and can be used at the same time as the other. The D-channel is used for sending information between you and the phone company to start and end calls.

The line gets brought to you on an RJ-11 modular jack (the same as an analog line). You plug your Terminal Adapter (TA) or router into the jack, and you can optionally plug a regular telephone or fax machine into analog output ports on the TA.

Can I really get 128kbps Internet access?

Yes. When you dial up OCS (ONLine Computer Solutions, Inc.) using a regular modem, your data gets converted to analog by your modem, sent on the regular phone line, and converted back to digital data at the other end. Because of line noise, modem incompatibilities, and "quantization" noise introduced by the digital-analog-digital conversions, you normally get 24.0kbps-44.0kbps in practice over a regular phone line and modem, and it varies from call to call (and through the duration of the call).

With ISDN on the other hand there is no digital-analog-digital conversion of any kind. The data remains digital as it traverses the ISDN line to OCS, and you always get the full 64kbps capacity of each of your two B-channels.

But aren't there 56kbps analog modems available now, which I can use on my regular phone line?

Modems that support the V.90 "56k" standard are now available, and OCS supports them in all of its larger cities. They do have disadvantages compared to ISDN:

These modems only support 53kbps in the download direction, and the upload direction is limited to 33.6kbps. Although many people download more than they upload there is little benefit from these modems for users who upload frequently, such as Web designers or frequent email correspondents.
These modems are subject to the same analog line noise problems as current modems. If you are not currently getting 33.6kbps connections across your phone line, you will not be getting 56kbps connections with the new modems.

ISDN is works exactly as advertised.

Is ISDN expensive?

ISDN costs somewhat more than two normal residential lines, but less than two business phone lines.

To connect to the Internet using ISDN you need to replace your modem with an ISDN Terminal Adapter (TA), but these are not expensive.

The OCS charges are also not significantly higher than for a regular modem dialup:

Are there other benefits?

Other advantages to ISDN over regular POTS lines/analog modems include:

Instant call setup. A normal modem takes 30-40 seconds to dial the phone, wait while it rings, negotiate with the modem at the other end, and start to exchange data. An ISDN call takes less than 1 (one) second to be completed!
Call bumping. If you are using both your B-channels to surf and someone calls you on one of one of their numbers, they do not get a busy signal, instead your phone rings! If you pick it up your TA will keep you connected to the Net using just the other channel. When you hang up, the TA will automatically start to use that B-channel also for your Net connection again. This is ideal for having a fax machine connected to for example. It also works the same way if you pick up a phone connected to your ISDN line in order to make an outbound call.

These features make ISDN ideal for the home office and small business environment, even without considering its super-fast Internet access capabilities.