For communication to take place between two people from widely different countries or cultures, an electronic or human translator is required to act as an interface between them. Similarly for a computer to communicate with another completely different system, this will also require an interface of some kind.

An interface is usually provided by a card which contains ports for input and output devices, plus processing and memory microchips. In effect it translates one form of communication from an external input device into that which can be understood by the computer and then, if necessary, into another that can be sent to any special output device, or another computer. An interface card may be inserted in one of the slots provided inside the computer or it may be external with its own power supply and plugged into the computer's serial communication port.

Here are some common examples:

MODEM (MODulator-DEModulator) - needed for Internet, email, fax and video-conferencing communications using telephone cables. It converts outgoing digital signals from the computer into analogue audio tones which can travel along the telephone wires, and the reverse for incoming signals.

A good modem can transmit and receive at a speed of 33,600 bits per second (bps) which is about 4200 bytes (or characters) a second. This is about one page of text, so it is much cheaper and somewhat quicker than ordinary mail.

Sound Card - for music or speech from programs, CD-ROMs, and microphone. It usually includes a MIDI interface for input from musical instruments.

MIDI (Musical Instrument Digital Interface) - needed to connect musical instruments to a computer so that the music played can be stored as a file, displayed on screen, edited, printed or played back.

Network Card - enables the computer to communicate with other computers linked together by cable through the interface. Used for shared storage of programs and work files, and for sharing printers.

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