UPGRADING REPAIRING PCs

Table 6.8 Modem Modulation Standards and Transmission Rates
Continued
Maximum Transmission
Protocol Rate (bps) Duplex Mode
ITU V.32bis 14,400bps (14.4Kbps) Full
ITU V.32fast 28,800bps (28.8Kbps) Full
ITU V.34 28,800bps (28.8Kbps) Full
ITU V.34bis 33,600bps (33.6Kbps) Full
ITU V.90 56,000bps (56Kbps) 1 Full
1. While the ITU V.90 (successor to the proprietary 56Kflex and X2 standards) allows for this
speed of transmission, the U.S. FCC (Federal Communications Commission) allows only
53,000bps (53Kbps) at this time.
56Kbps Standards
Virtually every modem sold today corresponds to one or more of
the so-called 56Kbps standards for faster downloading from an
Internet service provider (ISP). Uploading to a remote computer
must run at the slower V.34bis speeds.
Table 6.9 lists the original and final 56Kbps standards.
Modems 177
Table 6.9 56Kbps Modem Standards
Modem Chipsets Supported
Standard (Major Brand Example) Notes
x2 Texas Instruments First 56Kbps standard in use;
US Robotics not compatible with K56flex.
K56flex Rockwell Second 56Kbps standard in
Hayes, Zoom use; not compatible with x2.
V.90 All 56Kbps modems Official ITU standard has replaced
with updated firmware previous proprietary standards
listed previously.
V.92 New ITU standard Will allow higher upload speed (to
44Kbps), quicker access, and callwaiting
compatibility. Look for
products in late 2000 or early
2001. Might require new chipsets.
Because 56Kbps was originally a proprietary standard that was
chipset dependent, many early adopters have had problems getting
high-speed access as more and more ISPs have switched their x2- or
K56flex-specific modem pools to V.90. Table 6.10 provides guidelines
for upgrading your non-V.90 modem to the V.90 standard.