An analog modem for a PC can take the form either of an external device with its own power supply that plugs into a PC's serial port or USB port or of an internal expansion card you insert into a PCI or PC Card bus slot inside the computer. Very few ISA-slot analog modems are still on the market because the majority of recent systems no longer have ISA slots.

Most manufacturers of modems have both internal and external versions of the same models. External versions are slightly more expensive because they include a separate case and power supply and sometimes require you to buy a serial modem cable or USB cable.

Both internal and external modems are equally functional, however, and the decision as to which type to use should typically depend on whether you have a free bus slot or serial port, whether you have USB ports and Windows 98/Me/2000/XP, how much room you have on your desk, the capabilities of your system's internal power supply, and how comfortable you are with opening up your computer.

I often prefer external modems because of the visual feedback they provide through indicator lights. These lights let you easily see whether the modem is still connected and transmitting or receiving data. However, some communication programs today include onscreen simulations of the lights, providing the same information.

In other situations, however, an internal modem is preferable. If you are using an older computer whose serial ports do not have buffered UART chips, such as the 16550, many internal modems include an onboard 16550 UART-equivalent chip. This onboard UART with the modem saves you the trouble of upgrading the UART serial port.

Also, external 56Kbps modems can be hampered from achieving their full speeds by the limitations of the computer's serial port. An external USB model or an internal model using the PCI slot might be preferable instead. Not all modems that function at the same speed have the same functionality.

Many modem manufacturers produce modems running at the same speed but with different feature sets at different price points. The more expensive modems usually support advanced features, such as distinctive ring support, caller ID, voice and data, video teleconferencing, and call-waiting support.

When purchasing a modem, be sure it supports all the features you need. You also should make sure the software you plan to use, including the operating system, has been certified for use with the modem you select. If you live in a rural area, or in an older city neighborhood, your telephone line quality might influence your decision.

Look at comparison test results carefully and pay particular attention to how well various modems perform with noisy lines. If your phone line sounds crackly during a rainstorm, that poor-quality line makes reliable modem communications difficult, too, and it can limit your ability to connect at speeds above 33.6Kbps.

Another feature to consider is the modem's resistance to electrical damage. Some brands feature built-in power protection to shield against damage from digital telephone lines (higher powered and not compatible with modems) or power surges.

However, every modem should be used with a surge protector that allows you to route the RJ-11 telephone cable through the unit for protection against high-voltage surges. All modems on the market today support V.90 or V.92, and even if your particular location can't support those speeds, your modem might still offer advanced features, such as voicemail or simultaneous voice and data.

Keep in mind that V.90/V.92 connections seem to work better for many users if their modems also support x2. If you prefer a modem made by a vendor that also supports K56flex, try to buy a modem that contains both types of standards in its firmware (referred to by some vendors as "Dualmode" modems).

Upgrade

If you bought your modem in 1997 or later, or if it was included in your computer, chances are good that it came with 56Kbps support or that you've upgraded it to some form of 56Kbps support. However, even though today's V.90/V.92 modems still have the same maximum speed, other changes in modem design have occurred that might make a modem upgrade desirable for you.

And if you are still using a 33.6Kbps modem or even slower model, you should get a 56Kbps modem if your line quality can support it. Analog modems introduced from 2001 to the present still run at the 53Kbps FCC maximum with the potential to run at up to 56Kbps if the FCC regulations change, but they might offer one or more of the following advanced features:

• Call-waiting support

• PCI expansion slot for internal modems

• USB connection for external modems

• Faster performance for gaming

• MNP10 and MNP10EC

• V.92/V.44 support

WinModems

Modems without a UART chip, sometimes referred to as WinModems after the pioneering U.S. Robotics version, can save you money at purchase time but can cause problems with speed and operating-system compatibility later.

For users wanting an inexpensive internal modem, a modem that doesn't use a traditional UART instead of a UART-equipped internal or external modem looks like a great deal, often costing less than $40, compared to $80 or more for a UART-equipped "hardware" modem. But, there is no free lunch for modem users.

What can you lose with a modem that lacks a UART? First, you need to realize that there are actually two types of UART-less modems: those that rely on Windows and the CPU for all operations (these modems are also called controllerless modems) and those that use a programmable digital signal processor (DSP) chip to replace the UART.

Both types of modems use less power than traditional UART-based modems, making them better for use with notebook computers. Although both are "software modems," there's an enormous difference in what you're getting. A Windows-based modem must run under Windows because Windows provides the brains of the modem, a cost-cutting move similar to that used by some low-cost host-based printers.

You should avoid this if you're planning to try Linux, move the modem to a Macintosh, or use an old MS-DOS–based communications program. If you have no drivers for your modem/operating system combination, you'll have no luck using the software modem.

Software modems that lack a DSP have a second major strike against them: They make your CPU do all the work. Although today's computers have much faster CPUs than those required for typical software modems (Pentium 133 minimum), your modem can still slow down your computer if you multitask while downloading or surfing the Web.

Most of the modems bundled with computer systems are software modems, and the major chipsets used include Lucent LT (now Agere Systems), Conexant (formerly Rockwell) HCF, U.S. Robotics WinModem, ESS Technology's HSP-compliant chipsets, Intel's Modem Silicon Operation (formerly Ambient), and PCTel.

Except for U.S. Robotics, the other companies produce chipsets that can be found in the modems made by many manufacturers. For best results, do the following:

• Make sure your modem uses a DSP. Typically, these modems don't require a particular CPU or a particular speed of CPU.

• Consider modems built around the Lucent/Agere LT chipset. These modems have a DSP, and Lucent/Agere's firmware is frequently revised to achieve the best results in a rapidly changing telephony environment.

• Use the modem manufacturer's own drivers first. But software modems can often use any manufacturer's drivers for the same chipset with excellent results; in particular, Lucent/Agere LT chipset modems typically can use any Lucent/Agere LT driver from any modem manufacturer.

• Don't delete the old software driver when you download and install new modem software. As with UART-equipped modems, the latest firmware isn't always the best.

• Look carefully at the CPU, RAM, and operating system requirements before you buy your modem.

Many computer users today didn't install their modems, or even purchase them as a separate unit. Their modems came bundled inside the computer and often have a bare-bones manual that makes no mention of the modem's origin or where to get help. Getting V.90 firmware updates, drivers, or even jumper settings for OEM modems such as this can be difficult.

One of the best Web sites for getting help when you don't know where to start is the "Who Made My Modem?" page, which features:

• Links to the FCC's equipment authorization database (enter the FCC ID to locate the vendor)

• Using ATI commands to query the modem chipset

• Lookup by chipset manufacturer

• Search engine tips

• Links to major modem and chipset manufacturers

Squeezing Performance

Although many users of 56Kbps modems have seen significant improvements in their connect speeds and throughputs over their previous V.34-type modems, many have not or have seen only sporadic improvements. According to the research of Richard Gamberg, available online at his Modemsite, a combination of five factors comes into play to affect your ability to get reliable connections in the range of 45Kbps–53Kbps (the current FCC maximum):

• The modem

• The modem firmware/driver

• Your line conditions

• The ISP's modems

• The ISP's modem firmware

It's up to you to ensure that you match your modem 56Kbps type to the 56Kbps standards your ISP supports, and that you use the best (not always the latest!) modem firmware and drivers, as discussed in the previous section.

Other modem adjustments recommended by Modemsite include

• Modifying existing modem .INF files used by Windows 9x to accurately reflect connection speed

• Disabling 56Kbps connections (!) when playing games to minimize lag times

Telco

In addition to the well-known analog-to-digital conversion issue that prevents some phone lines from handling 56Kbps modems at anything beyond 33.6Kbps, other local telephone company (telco) practices and services can either prevent 56Kbps from ever working or take it away from you after you've enjoyed it for a while.

If you were getting 45Kbps or faster connections with your 56Kbps modem but can no longer get past 33.6Kbps, what happened? Some local telephone companies have been performing network "upgrades" that improve capacity for voice calls but prevent 56Kbps modems from running faster than 28Kbps.

The cause seems to be the telephone companies' change from a signaling type called RBS (Robbed Bit Signaling) to SS7 (Signaling System 7), which changes how data used by the modem for high-speed access is detected. Caller ID devices connected to your phone line use RBS or SS7 signals to obtain information from incoming phone calls.

If you use a caller ID box on the same phone circuit as your modem (even if it's connected in another room), you might not be able to get fast connections, or you might experience frequent disconnects. If you notice a drop in connection speed or reliability after you install caller ID, disconnect the caller ID box from the wall jack while you're online and see whether the speed and reliability of your modem connections improve.

What else can you do? You can install the latest firmware available for your modem model or chipset. You can also check with your local telephone company to see whether it can update its firmware to solve the problem.

Even if your modem has different firmware, checking on an upgrade might still be useful because this problem is likely to become widespread as telephone numbers, exchanges, and area codes continue to multiply like weeds and telephone network upgrades must keep pace.