When we talk on the telephone we generally transmit a message to someone else. The message is made up of words that we speak into the telephone instrument. The human voice causes sound to be formed into words; these sounds are transmitted in the form of acoustical wave patterns into the telephone instrument where they are translated into electronic wave patterns. These wave patterns are transmitted over a channel to their destination where they are converted back into sound waves received by the human ear. It may be mentioned that all electronic transmission takes place by means of wave patterns. There are two major patterns. They are analog and digital.