2.  It is the transmission of data from one place to another.  A data communication system is made up from hardware, software and communications facilities.  Can consist of computers connected on a global scale, or computers linked locally via computer terminals and other input/ output devices.  It doesn’t matter what type of data communication system it is, data transmission channels are NEEDED to carry the data from one place to another.

3.  Can be classified according to bandwidth.  The bandwidth determines the volume of data that can be transmitted at any one time.  The narrower the bandwidth, the less data it can transmit.  Narrowband and broadband are used to describe the capacity of transmission channels, although they are not very accurate.

4.  Refers to data transmission over a telephone line using an analogue modem.  Narrowband users connect to the internet via a remote computer.

5.  Refers to data transmission using ADSL (Asymmetric Digital Subscriber Line) and cables.  ADSL is a way to transfer digital signals using telephone lines.  Can be a lot faster than Narrowband.

6.  Fibre optic cables,  Coaxial cables,  Communication satellites,  Microwave links.