March 24, 1997
56K modems: Buyer beware
Make sure they work from your site
By Michael Caton

  PC Week Labs Review In initial tests of 56k-bps modems, PC Week Labs had difficulty connecting at the advertised throughput rate. In further tests, we managed to connect at these higher data rates, using modems from U.S. Robotics Corp., but we aren't changing our original recommendation: Make sure these modems will work from a given location before buying.

In tests performed by PC Week Labs and sister publications Windows Sources and PC Magazine, connecting at 56K bps with the U.S. Robotics $395 Courier V.Everything x2 modem and $219 Sportster 56K Faxmodem was limited more by phone line infrastructure problems than any fault of the modems. At any rate, the results were discouraging: We could connect at 56K bps only from about 55 percent of the locations we tried.

There are a few factors corporate buyers should consider before buying into the technology. First, the modems require a special switch at the point of service, instead of another modem. In our tests, we dialed in to a U.S. Robotics Total Control NetServer/8 I-modem switch at a U.S. Robotics site and at Windows Sources offices. Firms will need to buy either a similar switch to set up a modem pool or connect via an Internet service provider with one of these switches.

According to U.S. Robotics officials, the 56K-bps modems should work with 90 percent to 95 percent of phone lines. However, the analog-to-digital conversion that occurs at a PBX reduces throughput. For corporate applications, this means remote users dialing through a PBX (from a hotel or remote office, for example) are less likely than users telecommuting from their homes to see a high-speed connection.

When dialing in from residences in Boston, Florida, New York and Pennsylvania, we could connect to the U.S. Robotics and Windows Sources sites at data rates between 44K bps and 52K bps. When we dialed out through a PBX, we generally got a connection at 28.8K-bps or 33.6K-bps speeds.

Line quality also plays a role in the modems' performance. When dialing from two lines in an apartment in Boston, we saw connection rates ranging from 19.2K to 48K bps; using the apartment's older line, connection rates ranged from 44K to 48K bps, but we couldn't connect at higher rates than 19.2K bps using a recently installed second line.

The new 56K-bps modems have asymmetrical data rates, with the downstream rate being greater than the upstream rate, making them better suited for Web browsing rather than applications such as videoconferencing that require symmetrical data rates.

The Courier modem has flash memory, so it can be upgraded to support emerging standards. U.S. Robotics is offering a $60 flash upgrade to 56.6K-bps speeds for its 33.6K-bps Courier.

U.S. Robotics 56K-bps modems
U.S. Robotics Corp.
Skokie, Ill.
(800) 877-2677
PROS: Provide higher-speed connections than 28.8K- or 33.6K-bps modems. CONS: PBXes, however, limit connect speeds to the V.32 rate.
Summary: U.S. Robotics is first to the 56K-bps market with its Courier V.Everything x2 and Sportster 56K Faxmodem modems, but buyers shouldn't follow the company's example and rush in. The modems do deliver faster performance than previous-generation lines, but the types of sites from which users will be able to connect at high speed is limited. PBXes, in particular, will prove problematic for corporations.
PC Week Labs' scoring methodology can be found at


Copyright(c) 1997 Ziff-Davis Publishing Company. All rights reserved. Reproduction in whole or in part in any form or medium without express written permission of Ziff-Davis Publishing Company is prohibited. PC Week and the PC Week logo are trademarks of Ziff-Davis Publishing Company. PC Week Online and the PC Week Online logo are trademarks of Ziff-Davis Publishing Company.

Send mail to PC Week