Education And Debate


BMJ 1995; 311 doi: (Published 05 August 1995) Cite this as: BMJ 1995;311:381
  1. Nicholas Lee,
  2. Andrew Millman

    The international telephone network has over 400 million subscribers. This vast network can be used to connect even the most basic personal computer to any other computer or information system anywhere in the world. Most of these systems are available 24 hours a day, seven days a week and can be accessed very easily from home or work using simple and cheap equipment. This means anyone can tap into the world's accumulated medical knowledge at the touch of a button.

    Computers communicate internally by digital signals.Although these signals can be sent down a wire, the telephone network has been designed to carry speech-like frequencies.For computers to use telephone lines their digital signals have to be converted to speech frequencies. This conversion is carried out by a modem (modulator-demodulator).

    Selecting a modem

    There are several points to consider when buying a modem. Most countries allow only approved modems to be connected to their public telephone network. The stamp of approval guarantees compatibility. Because the standards vary manufacturers have to produce a specific modem for each country, although a pan-European standard is being discussed. It is no longer worth buying a modem that cannot also send faxes.

    Configuring your communications program to match a given modem can sometimes be difficult, but it is much easier if the modem you purchase is directly supported by the software. The quality and ease of access of technical support varies, and good support from a British or locally based company is of great help when problems arise. The performance of modems varies considerably depending on two main factors: the basic speed of the modem (quoted as the Baud rate) and data compression.

    What you need to link up to other computers

    Computer—Virtually any computer, provided it has a serial port


    External—Mains powered unit with a speaker and visual display unit to show status of modem

    Internal—Slots directly …

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