Questions and Answers

What you should know about modems

This article tells you what modems do, and explains different types to help you choose and use a modem.

External Modem A modem (modulator/ demodulator) converts (modulates) data into signals which can be sent down a phone line. It also converts (demodulates) incoming phone line signals back into computer data.

The faster the modem operates, then the shorter the time it takes to send an E-mail, a computer file or browse a web site. Faster modems save you time and help reduce the cost of a call. A modem call costs just the same as an ordinary phone call (i.e. about 5p. minimum per BT call) unless you opt for a special Internet price tariff.

However, you can only go as fast as the slowest part of the communications chain, and there is little you can do to speed up the "remote" connection beyond your control. Speed also falls when the Internet gets busier, notably when the USA wakes up and goes on line. But speed and reliability are much better now than they have ever been.

The maximum theoretical speed obtainable with current modem technology is 56Kbps - 56,000 bits (binary digits) per second. A V.90 compliant device can in theory operate at this speed, but may drop down to a slower speed when negotiating a connection. Less than 50Kbps is usually obtained in practice. Slower modems may operate at a bit rate of 28.8 or 33.6 Kbps. The latest standard is V.92, which is no faster but lets you accept incoming calls even when your modem is online. No ISPs support this yet.

I'm Baud

For the technical reader — a modem's baud rate is not technically the same as its bit rate. The baud rate determines how often the modem carrier changes state per second: the modem's overall speed is determined by how many bits are sent/ received per transition = baud rate × bits per baud. Think of a modem "squirting" out so many bits of data during each baud transition. A device operating at say 2,400 baud and allowing 12 bits per baud, would have a transmission speed of 28,800 bps. Old modems could only work at one bit per baud, so a 300 baud modem ran at 300 bits per second. It is probably for historical reasons that people think that baud rate is the same as bps, but at the end of the day it's the latter bps figure which interests us all. Much effort goes into compressing more data into each baud, to increase modem speeds.

A Window® Dial-Up Network icon can tell you the number of bits per second, plus the number of bytes sent and received. (Place the mouse pointer over the dial-up icon in the Windows system tray to see.).

Internal/ External Modems

Modems are either internal (fitted within a computer) or external (working outside of the main computer).

Internal types for PCs are usually PCI (Peripheral Component Interconnect) Plug & Play cards which are easy to install. They may not be as good as an external type.
External types mostly use a PC's serial or USB port and need a mains adaptor. They are sometimes called "hardware" modems because they contain everything needed to process the signal, unlike a "soft modem" which needs software.

Something called a "Winmodem" will only operate in conjunction with a Windows® computer, and cannot act as a stand-alone modem. Winmodems are cheaper but arguably less powerful as they depend on the computer's operating system for signal processing. Manufacturers of USB modems include Modular Technology and Zoom Telephonics. See our Suggested Links page for web addresses and URLs of modem manufacturers.

Tip: Once you own a modem, it is worth keeping an eye on manufacturers' web sites, as new modem drivers may sometimes be released which may help improve performance or reliability. You must check the instructions for modem upgrades very closely: some types are "flash" upgradeable (which re-programs the modem's internal chip) and will be damaged if the wrong "flash" upgrade is used.

Fax Modems

A fax-modem can also be used to send or receive paperless faxes direct from a computer, instead of printing and feeding through a traditional fax machine. A new class of fax-storage modem can actually store incoming faxes, even when the host PC is switched off. Olitec and 3COM both make them.

Voice/ Fax modems incorporate a digital answerphone as well, and may have all-in-one voicemail, off-line fax and data functions making them a perfect choice for the Small Office/ Home Office user using one phone line.

Another use for modems is in dialling into a Bulletin Board System (BBS) to obtain files - noting that you pay ordinary phone rates (including international rates where necessary), not local dial-in rates. A terminal program (e.g. Windows® Hyperterminal) is needed. This enables direct communication between two computers rather than over the Internet.

Dialling a BBS is also a good way of testing a modem, since direct modem-to-modem communication is the simplest possible technique and it bypasses the Internet. If you can access a BBS, then you know your modem is installed and working correctly.

In some areas you could try a cable modem if a cable service is availble. These provide high speed always-on access for heavier users. Or consider ISDN, which uses an internal ISDN card or a TA (terminal adaptor) instead, and can offer higher speeds for heavy users, but is more expensive. In the future, ADSL (Asymmetric Digital Subscriber Line) will offer vast increases in speed and bandwidth but is much more expensive to use.

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