Most of us find telephones extremely useful for talking to others, but the telephone has several other uses. The telephone network sends voices around the world in the form of electric signals. It can also send other kinds of electric signals that are not voice signals for example, computer signals.
Computer networks are groups of computers connected together by telephone lines. They link computers in business, but you can link your home computer into networks to get information and computer programs of all kinds, and to send messages to other computer users. It’s also possible to send pictures over the telephone with special machines that convert the pictures into easily transmitted electric signals.