“What modem should I buy?” is a very common question hitting the sales and tech support channels here at TurboPower. Those of you asking the question probably noticed that we had a hard time giving you a straight answer. In fact, we probably did our best to avoid the answer altogether. 

Why? 

We at TurboPower do our best to give quality answers to your questions. This particular question is difficult to answer with any reasonable amount of accuracy. 

It’s a jungle out there…

The modem market is extremely dynamic and competitive. Any modem we recommend on a given day may not exist the next day (if the modem does exist, it may be different internally than the one we have in our lab). Indeed, the manufacturer of our recommended modem may not exist the next day. Those of you keeping an eye on technology news probably noticed that some of the “big boys” in the modem business (such as Motorola and Hayes) closed up shop over the last year or two.

This level of competition has driven margins down to a bare minimum. Unfortunately, the competition seems to be primarily based on price and feature set. Sure, competition is good, but not when it gets to the point that corners are cut. We’ll mention some specifics about these “cut corners” a bit later.

We Only Know Enough to Realize We Don’t Know…

The communication engineers here at TurboPower know a good deal about modems – and we understand that you look to us for hardware advice for exactly that reason. We’ve worked with many brands and models, studying them in detail – we’ve learned their quirks and how to deal with them as much as possible. It makes sense that we should be able to tell you what works and what doesn’t, right? Wrong.

You see, the more we learn about modems, the more we realize how tough the situation is. We know that there are variations in the hardware and firmware used in the modems – even modems with the same exact make and model number. We know that these variations may not be public knowledge – the details of such variations are often kept within the walls of the modem maker. We also know that with modems, like any other piece of hardware, there are variations in quality due to an imperfect manufacturing process. Granted, the variations are usually kept to a minimum when you deal with the more respected manufacturers, but they exist nonetheless. Our experience has shown us that even top ranked manufacturers can have a bad day (or batch).

Is the situation hopeless? Well, no. To be honest, most modems work reasonably well most of the time – so there’s no need to panic. Arming yourself with a bit of knowledge before venturing out to the nearest computer store is worth the effort though – it’ll increase your chances of getting something with a reasonable level of reliability. 

Quick Lesson – Modems 101…

What exactly is a modem, anyway? Well, even that is hard to answer these days as it’s become a bit of a marketing term. As an example, in the United States we have a new telephone service called DSL – the device use to connect the phone line to the computer is called a modem, but it’s really more of a network router. Strictly speaking, a modem is a MOdulator/DEModulator. It converts digital signals from the computer’s serial port to modulated analog signals for the phone line (and vice-versa).

The term “modulated” or “modulation” refers to the technique of combining information (the data from the serial port) with a carrier wave that travels well through the target medium (the phone line). The carrier wave for a standard phone line is usually restricted to audio frequencies, since that is what the phone line (and associated equipment) is designed to handle. Modulation also makes things like radio and television possible, the carrier wave there being very high and ultra high frequencies that can travel through air/space.

Besides the basic modulation/demodulation, a modem has a lot of other jobs to do. It needs to be able to properly connect with a modem on the other end of the line – negotiating things like the type of carrier to use as well as the type of error correction and data compression to use. Once a good connection is established and data starts flowing; the modem dynamically encodes, decodes, compresses, decompresses, modulates, and demodulates the data – all while checking the data for errors (requesting a resend of any data that has errors). That’s for simple modem communications, things like faxing and voice communications add more factors to the equation.

The good news is most of this work is done without your knowledge (or even APRO’s knowledge). Just keep in mind that it’s a complex process, and things can easily go wrong. 

What Should I Buy?

Here are some general guidelines we can offer. Remember, these are only general guidelines. We have several modems in our lab that break one or more of these guidelines and still work fine. We also have a couple modems that follow all the rules and are problematic.

We recommend avoiding Winmodems and RPI modems, otherwise known as software modems. These modems offload some of the “smarts” of the modem to the host computer. They use software drivers to handle things like compression and error correction that are normally handled by the hardware/firmware in the modem. To be fair, these modems have a couple advantages – the drivers are easy to update, and the overall cost of the modem is lowered (the whole concept of a software modem probably came about as a result of the competition in the modem market).

 In our view software modems have several disadvantages, for example: 

-          The host computer is forced to donate resources in support of the communications session (not only the CPU, but also memory, data bus, power and so on).

-          Shifting these duties to software results in an overall loss of efficiency (custom hardware is better suited to handle this type of processing).

-          The modems are tied to the operating system. They currently do not work in alternate operating systems such as Linux.

-          The software drivers that support these modems are proprietary, and cannot be used directly without license. For this reason, APRO does not have access to the error correction and compression features of these modems unless the modem is accessed through Tapi.

How can you tell if a modem is a software modem? Usually, you’ll see “Winmodem” or “RPI” somewhere on the box. A fairly comprehensive database of modems that identifies software modems can be found at http://www.o2.net/~gromitkc/winmodem.html. This website also has additional information about modems, as well as useful links to other modem websites. 

We recommend using external modems. This is simply the best way to ensure you get a modem with all its brains intact. As far as we know, it’s not practical to produce an external modem that uses drivers to handle things like error correction and compression. An external modem is also easier to monitor and troubleshoot (most have status indicator lights on the front panel). External modems have their own power supply – so it’s not an additional load on your computer’s power supply. External modems are often easier to install and set up, since you don’t have to open the computer case and deal with system settings such as IRQs. Admittedly, this situation has improved somewhat with innovations like Plug and Play – but that’s not available with all operating systems.

We recommend against “chasing the latest technology”. Modem makers often race to hit the market first with a new feature in order to gain market share. It often takes a little while to get new features reliable though, so the first few batches of modems sporting a brand new feature often aren’t as reliable as subsequent batches will be.

We recommend getting a modem with the features you need, and no more. In other words, if you need a modem strictly for faxing, why get a voice modem? This is a cost saving recommendation for the most part, but there’s a certain “less can go wrong” issue also.  

We recommend getting a modem that supports more than one fax class if you’ll be faxing. We’ve found having options in this area is a good thing – if one of the available standards doesn’t work for a given situation, another option often will. APRO currently supports Class 1, Class 2 and Class 2.0 faxing. 

The fax class defines the communication between APRO and the modem. Class 2 and 2.0 modems handle more of the work themselves, with only minimal communication required between APRO and the modem. This is usually an advantage, because the modem handles most of the work (similar to the advantages mentioned above in the software modem discussion). A potential disadvantage with Class 2 & 2.0 faxing is that APRO is “kept in the dark” during large portions of the fax session. Obviously, this isn’t a problem if the fax session goes well – but if there are problems during the session, APRO has limited ability to detect, correct, and log the situation. 

With Class 1 modems, APRO is intimately involved with nearly all aspects of the fax session. As stated earlier, this loads the system more – but if things go wrong, there are more options available to correct the situation. 

We recommend using well-known brands. It’s tough to know for sure if the maker of your modem will still be around in a year or two in the event you need a new driver or support for your modem. The odds seem to be a bit better if you stick to an established brand. 

Buy from a store with a reasonable return policy. This should allow you to test the modem in the environment (and with the application) you’ll be using. 

If you need to buy many modems for a project, buy one or two first and test them thoroughly with the code you’ll be using before committing the money for all of them. This only makes sense. If you’re going to be buying a couple hundred modems, make sure you’re getting modems that will work well in your situation.

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Last updated: July 22, 2003.