Getting the Most Out of 56 K Modems

by Brian McConnell

In just a few years, the worldwide web (and the internet in general) has grown from an obsure academic research tool to a basic requirement for conducting business. Web applications are growing ever more complicated, and require even more bandwidth than before. While computing power has increased exponentially and prices have fallen, chances are, you are still connecting to the internet through the slowest possible means, an ordinary, plain old phone line.

Modems (short for modulator/demodulator) convert digital data into an audio signal (sound) which can be carried over the public telephone network. The telephone network was designed to carry human speed, not computer data. Hence, an entire industry has developed around the need to allow computers to "talk" to each other over the telephone network.

Early modems operated at slow speeds, typically 300 baud (bits, or digits, per second). At this speed, you can transmit 1 to 2 lines of typewritten text per second. In the past 10 years, modem speeds have increased dramatically, from 300 to 1200 baud, to today's high-speed dial-up modems, which deliver speeds up to 56000 baud, about 100 times as fast.

The latest, fastest dial-up modems can transmit up to 56,000 bits of information per second. While this might sound fast, this speed is still about 200 times slower than a typical office data network, and about 2000 times slower than a high-performance data network. The new high-speed modems, generally referred to as 56 K modems, push the telephone network to its theoretical limits. These modems deliver speeds up to 56,000 bps (bits per second, or 56 Kbps) downstream (from your internet service provider to you), and up to 33,600 bps upstream (from your computer to your internet service provider (ISP).

Double the speed on the same phone line? Sounds good, what's the catch?
While this all sounds great, twice the speed of a conventional modem on the same phone line, there's a catch. 56 K modems push plain old phone lines to their theoretical limits. Because of this, these modems are extremely sensitive to anything that degrades the quality of the connection between your computer and your ISP. If they encounter the slightest problem, they fall back to a slower speed, typically around 28,000 bps, roughly half of the maximum speed.

The trick to maximizing 56 K modem performance is making sure you have a really clean connection between your computer and the outside telephone network. The following tips will help you do this, and therefore improve your connection speeds.

Tip #1 Do not connect your modem to a phone system
If you are using a telephone system in your office, do not connect your modem to the phone system, but instead connect it directly to an outside line. Almost without exception, connecting a 56 K modem to an extension on a phone system, instead of an outside line, will degrade your connection speed by at least 40 to 50%.

Tip #2 Do not daisy chain devices or modems
Avoid daisy chaining many devices together to share an outside line. While this works fairly well for older, slower modems, it weakens the signal enough to degrade connection speeds. Use a line share device instead. More on this in a minute.

Tip #3 Check your wiring for glitches and radio interference
Connect a standard phone to your outside line(s). Make some test calls to outside phone numbers. Have the called party (on the other end of the line) put you on hold. When the line is silent, listen carefully for static and for background noise. Radio interference is pretty common on phone lines (long cable runs sometimes act like radio antennas). If you pick up radio interference, an RFI filter (available from distributors like Hello Direct), will help resolve this problem.

Tip #4 Use a line share device
Line share devices allow you to connect many modems to a smaller group of shared outside lines. They work in the same way a PBX or key system allows voice users to share a smaller group of phone lines, except they are designed to optimize modem performance. Depending on the number of lines you need to connect, these will handle anywhere from 24 modems to dozens of users. One particularly good company is Line Share Devices.

What if 56 K isn't fast enough?
If you're interested in videoconferencing, transferring large files, or have many users sharing your internet connection, an analog internet connection isn't fast enough. You should look at high-speed digital telephone lines such as ISDN and ADSL.

Read "Getting Connected: The Internet at 56K and Up"