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I anticipate adding a list of WinModems that are known to work with Linux, particularly with Vector Linux, on this or a linked page. If you know of any, please add them to this page (or provide a pointer to appropriate pages elsewhere) even before this page is "completed". I think we want to identify them both by chipset (Manufacturer and model) and modem manufacturer (and model).

See connecting to the Internet.

There are at least two things to consider when choosing a dial-up modem -- type and speed.

List of desirable illustrations -- CFKVolunteers please see UsingTWikiAsCfkDocumentation:

  • An external modem
  • An internal modem (or two -- ISA and PCI, with enough view of the connectors to develop an initial feel for the difference in size and quantity of pins) (maybe both in the same picture)
  • A USB and a serial cable, or especially the ends to develop a quick sense of which is which


Modem Standards

Dial-up modems send data over a telephone wire in a particular pattern so that the modem and computer at the other end can understand what is being sent. (Think of it as similar to Morse code -- if somebody sends you Morse code but you don't understand it, you won't get the message.) I could get slightly more technical here and mention that the computer uses one code to communicate to the modem, the modem translates this into another code to communicate with the other modem.

In general, you don't have to pay too much attention to these standards, because most modems sold today are built in accordance with a standard and most of those standards are backwards compatible.

And, at the beginning of a modem connection there is a negotiation phase, during which the modems on each end of the connection will attempt to agree on a protocol (standard) that both can understand.

But, in any case, see buying computer equipment.

When a better or faster modem technology is developed some modems may be sold before a standard is agreed upon. Generally today, if a manufacturer starts selling a modem with a new technology that is not yet part of an agreed upon standard, he will provide you some way to upgrade to the standard later, when it is finalized.

There is a chance that you will buy (or be given) an old modem that does not meet the standards -- make sure you read buying computer equipment before purchasing anything for your computer.

I'll mention a few standards that may be of interest if you buy a new modem in the near future:

  • V.92 (often pronounced "vee dot ninety two") -- the latest standard, about 2 years old -- speeds up to 56 kbps (the same as V.90) but the neat thing is that it can work with the telephone company's call waiting feature. This allows you to briefly interrupt your computer's connection to the Internet to take another (brief) telephone call and then let you resume the connection to the computer without redialing. With this feature it is more feasible to use a single telephone line for both your normal voice telephone and for your computer's connection to the Internet. Your ISP must have V.92 modems and proper support to allow this feature to work.

  • V.90 -- the previous standard, allowing speeds up to 56 kbps. It should be noted that even though such speeds are allowed (1) the FCC limits the maximum connection speed to something slightly less than this, and (2) achieving this speed depends on ideal conditions, one of which is that your ISP has equipment located in your local telephone company's office so that one of the connections to the modem is digital. I'm not sure that is stated completely accurately (or well).

Usually a modem that is compatible with a modern standard is also compatible with all previous older standards. In other words, a modem that is compatible with V.92 is also compatible with V.90.


Modem speeds are specified in kbps which stands for kilobits per second. It usually takes about 10 bits of information to send one alphabetic character (like this "A"). That is a good guideline for plain text -- pictures graphic files require many more bits -- some graphic files may require 24 bits (or more) for each pixel (dot) in a picture, and even a small picture (an icon) may have 4096 dots (64 x 64), thus taking up approximately 100,000 bits (4096 x 24). This is why plain text web sites will load much faster than web sites that include graphics.

When discussing download speeds you should understand that all information on the Internet is passed from one computer to another multiple times to get from its source to its destination. See <somethingHops>?

Modems are specified in terms of the fastest speed they can achieve, under ideal conditions. All modern modems automatically negotiate at the beginning of a call to establish a connection at the fastest possible speed for the particular combination of modem quality, line length, and line quality (which can change daily or hourly because line quality can be affected by weather conditions).

Also, during a call, if the error rate starts to increase, the modems may renegotiate and drop to a slower speed to reduce errors. I don't know under what circumstances, if any a modem will attempt to renegotiate in hopes of going back to a higher speed?

There are some fairly technical aspects of setting up an Internet connection over a dial up modem that affect the performance, like the MTU (??). (In general, this is the packet size that you send -- other equipment in your connection maybe able to handle only smaller or larger packets -- if you send packets that are too large, they are broken up downstream (and headers added) decreasing efficiency. If you send packets that are too small, efficiency is reduced because of the excess quantity of packet headers.)

I use a 33 kbps modem for a few reasons:

  • I've tried the faster 56 kbps modems, and, where I live, I rarely achieved a connection faster than about 33 kbps (and then only 36 kbps) and sometimes achieved 24 kbps or less. (YMMV)
  • My modem is installed in an Internet gateway computer that is somewhat older and has only ISA bus slots.

We should do some checking with local ISPs -- some ISPs may have a stated minimum modem speed. (I know they don't want to deal with 300 bps modems.) I'm guessing that modems in the speed range 9.6 to 56 kbps are acceptable and can provide acceptable performance, recognizing the 9.6 kbps is fairly slow.

To summarize:

  • because of my location, I would not buy a modem faster than 33 kbps unless it cost the same or less than a 56 kbps modem (and it was made for an ISA slot).
  • if I did not have and could not afford a modem, I would accept a modem as a gift only if it was 9.6 kbps or faster (and if it was of a type I could install and use -- see the next section)

Modem Types

Internal vs. External

An internal modem is installed inside your computer. It obtains its power from the computer's power supply, and the telephone line is connected to a connector on the back of the computer.

An external modem comes in a (small) separate standalone enclosure. It usually also has a separate power supply (wall wart). The telephone line connects to the modem, and a special cable (serial or USB) is connected between the modem and your computer.

An external modem has the following characteristics which can be considered advantages or disadvantages depending on your point of view:

  • The case and external power supply take up extra space and an extra electrical outlet.
  • External modems generally have indicator lights (on the front of the case) that are always visible to help you keep track of what is going on (are you connected, etc.) Software is available for internal modems to make similar indicator lights appear on your computer screen.
  • If a lightning strike or electrical surge travels through your telephone line and damages your external modem, it is less likely to also do any damage to your computer. (In any case, if you have a modem, you should have appropriate surge protection installed.)

Software vs. Hardware

In recent years, modem manufacturer's have found ways to make less expensive modems by performing some of the modem's functions in the computer the modem is connected to rather than in the modem's hardware.

In other words, computer software performs some of the functions formerly performed by the modem's hardware.

Some people distinguish betweem these two types of modem by referring to one as a hardware modem and the other as a software modem. It would be nice if manufacturers did that as well, but they ususally don't, and you must usually figure it out for yourself. (We will try to give you the necessary clues on this page.)

Further, some users (not manufacturers) refer to a software modem as a Winmodem and/or a Linmodem. A Winmodem is a software modem that works only in Windows. A Linmodem is a software modem that works in Linux (and almost always has the software to work in Windows as well). Again, manufacturers do not make it that easy for you, and you have to read the box very carefully and have some other clues to distinguish a software from a hardware modem. We will give you helpful clues on this page.

<recent refactoring pass stopped here>

The problem with most software modems (and the reason they are called Winmodems) is because initially, at least, the software to perform the functions no longer performed in the modem hardware was written for Windows only. A software modem with only Windows software available is known as a Winmodem and can only be used on a Windows based computer.

In some cases, the manufacturer (or a dedicated hobbiest) has provided the necessary software to make a software modem work under Linux. In that case it is sometimes called a Linmodem. (And note that a Linmodem is usually (always?) also a Winmodem.)

Digressing on this for a moment, the best situation is if the manufacturer provides the necessary software, and it's even better if he provides it under an open source license -- thus, as long as he's in business you can get support from him -- if he goes out of business the source code for the necessary software is available and can be modified by a qualified person to solve any new problems that may be discovered. Generally, when a hobbiest creates a driver he does provide the code under an open source license. Note that he is doing a favor for everybody, and when you have a chance, please support the open source / free software movements.

Initially, only internal modems were manufactured this way, but now I think some or all of the USB modems are also software modems.

Bus Type

Computer cards installed inside a computer plug into a hardware connector that is also known as a bus (or a slot in or on the bus. (Or the standard that determines what that hardware connector looks like and how it works is known as a bus?)

There are some standardized buses, and some buses that are very proprietary. Apple computers use their own buses, not compatible with PC buses (sp?) (AFAIK).

Some buses that have been used in computers over the years include:

  • S100 (obsolete)
  • MicroChannel (an IBM proprietary bus that is pretty much obsolete)
  • ISA -- the first standard bus for the PC (the (IBM compatible) Personal Computer -- the thing that we almost all use today) -- still in common use, but gradually being superceded by the PCI bus
  • PCI -- the modern standard bus for the PC -- significantly faster than the ISA bus

What of all that is important to you?

  • When you buy an internal modem, it will plug into the bus -- you must make sure that your computer has a free slot of the proper bus type to install your modem.
  • AFAIK, all ISA bus (internal) modems are hardware modems, not software, Win, or Linmodems.
  • I'm not as sure about this, but I think that almost all PCI bus (internal) modems are software modems, only some of which (Linmodems) will work in a Linux computer.

Some Hints for Use

The Speaker

Both internal and external modems include a speaker, with means to tell the computer when to turn it on and off. I keep the speaker on in my internal modem while a connection is being made -- I've learned to recognize some problems by the sounds I hear (and you can too). (Generally speakers in an internal modem are not as loud as speakers in an external modem, but the sound level can be adjusted via software.)

An Extra Telephone

With either an internal or external modem, you can plug a telephone in after the modem. I have a very cheap telephone connected like that because it sometimes helps to pick up the phone to see what is happening (like is there a busy signal?). Depending on the modem, picking up the phone like this may break the connection.


External Serial Modems

An external serial modem is the one most often recommended for use with Linux, because any external serial modem will work with Linux. Unfortunately, it is also the most expensive modem, ranging in cost from $50 to $200.

It is easy to buy. At one time we could have said that you could buy any external modem and use it on a PC running Linux (ignoring very proprietary modems like those for the Atari 800XL). Unfortunately, nowadays (what a word!), there are external modems that connect to your computer via the USB bus and these are not compatible with most of the computers distributed by CFK (at this time).

In any event, see buying computer equipment.

External USB Modems

Internal Hardware Modems

Internal Win and Lin Modems


  • () RandyKramer - 09 Feb 2003
  • <If you edit this page: add your name here; move this to the next line; and include your comment marker (initials), if you have created one, in parenthesis before your WikiName.>

Topic revision: r1 - 2003-03-17 - RandyKramer
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