What are External Modems?

R. Kayne

External modems are communication devices that computers utilize to connect to public networks like the Internet. A modem that sits inside the computer is called an internal modem, while modems that sit exterior, are external modems.

External modems are communication devices that connect a computer to the Internet.
External modems are communication devices that connect a computer to the Internet.

The type of modem you require depends on the type of Internet access service you desire. There are two general categories: Basic dial-up service, and high-speed broadband service.

Acoustic couplers -- which send and receive computer data through telephone lines -- preceded modern modem technology.
Acoustic couplers -- which send and receive computer data through telephone lines -- preceded modern modem technology.

Basic Dial-Up (Internal and External Modems)

Traditionally, internal modems have been dial-up modems that connect to Internet service providers (ISPs) using an analog signal over a telephone line. Since telephones also use analog signals, phones and modems cannot share lines simultaneously. Dial-up is the slowest, but also the least expensive way to connect to the Internet.

External modems can also be dial-up modems, and if so, will be rated at a transfer rate of 56 kbps (kilobytes per second), like their internal twins. They are handy when there are no available internal slots, or if the modem needs to be shared between computers that are not networked. In this case, an external modem connected to a desktop system can easily be disconnected and connected to a different desktop, or even a laptop.

External modems for dial-up service are inexpensive and available everywhere computers are sold. They are easy to setup, come with instructions, and most include fax capability at the software level. Recent versions of most operating systems recognize and load drivers for dial-up modems, which are plug-and-play devices.

High-speed Broadband Modems

Most external modems today are not dial-up modems, but broadband modems. Those designed for broadband service provide a different kind of Internet connection that is extremely fast, used with high-speed ISPs. Broadband modems typically have transfer rates from 1.5 — 8 mbps (megabytes per second), or higher.

DSL, FiOS, cable and satellite are different flavors of high-speed Internet. Normally ISPs selling broadband Internet access will provide their customers with external modems pre-configured to use with the service. Depending on the contract terms, the modems might be leased with a small monthly charge, or provided free to use for the duration of the client's contract. High-speed modems are normally not internal.

Broadband modems can be wired, or wireless. If wireless, a wireless network adapter must be installed in each computer that is to communicate with the modem. These adapters can be PCMCIA, or external devices that attach to the computer via the USB port.

DSL modems utilize the telephone line for sending digital signals rather than analog signals. Consequently, you can use the telephone while using DSL service. This is also true of FiOS service, which uses fiber optic lines in place of standard copper telephone lines. External modems used for high-speed cable service will not use the telephone line, but rather the cable TV line. Local cable companies provide cable Internet service, where available.

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Discussion Comments


I have a small home office with two analog phone lines. Whenever the first line is busy the second line will obviously ring and I can put one on hold to answer the other. I setup two new generic (HERO) USB modems on two of my desktop PC's recently so I can fax out from my PC's and now I can't receive or make calls out on the second line. It's almost as if the second line were being blocked by the modem.

When I removed one of the modems from one of the desktops to test it and plugged my phone line back into the wall, the second line works just fine. Any idea what the problem could be?


I have an international student coming to stay who will require internet access and I do not wish for them to use the home internet service. They will also be required to use the internet at University. What is the best equipment that I should purchase for them to use? Thanks.


I have a computer that only has an ethernet jack. I already have an external modem for this computer that has a ethernet and phone jack. I was wondering if there was any way I could use the ethernet cord from the computer to the external modem and then connect the modem to the phone jack. Let me know if you have any suggestions for dial up. Thank you.


Yes. You can buy a broadband modem from a retailer and use it with the service, or get one with the service on a "lease" where it must be returned at the end of the contract period (i.e. when you quit the service). If you "lease" a modem it will be configured for you ahead of time. If you buy one, you'll have to configure it yourself to work with your service. Most modem manufacturers list which broadband services their modems will support, and Zoom DSL modems (for example) come with manuals that suggest the most common setup or configuration for the most popular broadband services. In any case, you don't need an internal modem.


I have a computer with no internal modem. If I order broadband internet, will the modem I purchase be enough for the broadband?

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