Radio College | Reading Room: Articles

Getting Audio to the Web

by Glen Johnson

xDSL, ISDN, Cable, 56k modem. All offer access to the Internet. The differences are speed, cost and availability. Let's go through them one by one.

"xDSL" refers to a class of technologies called Digital Subscriber Line. The "x" stands for any one of a number of implementations:

A = Asymetric (ADSL)
H = High-bit-rate (HDSL)
S = Symmetric or Single-line high-bit-rate (SDSL)
V = Very-high-bit-rate (VDSL)

ADSL is a constant, full time connection to the Internet. No dialing, no busy signal. It offers download speeds of up to 8 megabits per second. It's hundreds of times faster than a standard 28.8k modem. Upload speeds of up to 1 megabit per second. This is great for most users that want high speed downloads and don't need high speed uploads.

SDSL is a constant, full time connection. Uploads and downloads are a the same high rate of speed. It offers uploads and downloads at speeds up to 1 megabit per second.

xDSL varies in availability. Some areas offer only one or two types of xDSL access. In the metropolitan Detroit area where I live, Ameritech offers ADSL for $50 per month. Other ISP's offer SDSL for about $120 per month.

ISDN (Integrated Service Digital Network) is a dial-up connection. ISDN is a high-speed data service capable of transmitting at speeds up to 128k. That's roughly four times faster than standard 28.8k or 33.6k modems. ISDN allows you to surf the Net while simultaneously using he same line to make voice or fax calls. An ISDN line requires a digital device called a terminal adapter. ISDN is available in most areas. The cost in my area is about $35 per month.

56k modems promise the highest speeds over standard telephone lines. But independent tests show that they're routinely 20-25% slower in real-world situations, due to the susceptibility of analog lines to signal conversion erros and line noise. 33.6k modems "fall back" to even slower speeds. ISDN, on the other hand, was designed from the start to provide digitally pure connections. ISDN consistently delivers true 128k speeds.

Cable modems. Cable offers a constant, always-on connection to the Internet. The speeds vary from area to area. Cable is usually in the same speed category as ADSL or SDSL. It can be faster or slower depending on available bandwidth. The number of people in your area that share bandwidth deterimines the available bandwidth.

Cable is a bit like a party line or like a pipe. If only a few people are using the pipe, everybody gets great service. The more people using the pipe the slower things get. There are also security issues. Everything is in this big pipe. Someone could access the information you are sending or reciving or possibly, your computer (remember the connection is always on).

Glen Johnson is a Software Trainer, Web Designer and Network Consultant.