You tap on a membrane suspended above a steadily flowing jet of water. The air under the membrane causes slight deflections in the jet of water. A laser is aimed at a receiver. The jet of water flows through the laser beam, deflecting it from its target. Every time the movement of the air deflects the water jet, the laser beam hits its target. The laser receiver is connected to a computer, which takes each ‘hit’ and turns it into a 1 and each miss and turns it into a 0. The computer sends these etc. etc……

You get the idea: the air waves, the jet of water and so on are all channels. The words channel and medium are often used interchangeably, if slightly inaccurately. The choice (a pretty stupid one above) of the appropriate channel is a vitally important choice in communication. It’s obvious that you don’t use the visual channel to communicate with the blind or the auditory channel with the deaf, but there are subtler considerations to be taken into account as well. A colleague of mine was clearly much more responsive to visual communication than I. To elucidate his arguments he would inevitably grab a pencil and a piece of paper and sketch out complex diagrams of his arguments. Though they may have helped him to clarify his ideas, they merely served to confuse me, who would have preferred a verbal exposition. It’s curious that in the college where I work many students who are dyslexic or have other learning difficulties end up studying information technology in so-called flexible learning centers. Bearing in mind the statement above that “the choice of the appropriate channel is a vitally important choice in communication”, it’s less than obvious how a student who has difficulty reading and writing can have their needs met by a learning model which boils down in essence to ‘read this; it will tell you what to write’.