1. An information source. Presumably a person who creates a message.
2. The message, which is both sent by the information source and received by the destination.3. A transmitter. For Shannon's immediate purpose a telephone instrument that captures an audio signal, converts it into an electronic signal, and amplifies it for transmission through thetelephone network.
4. The signal, which flows through a channel. There may be multiple parallel signals, as is the case in face-to-face interaction where sound and gesture involve different signalsystems that depend on different channels and modes of transmission. There may be multiple serial signals, with sound and/or gesture turned into electronic signals, radio waves, or words and pictures in abook.
5. A carrier or channel, which is represented by the small unlabeled box in the middle of the model. The most commonly used channels include air, light, electricity, radio waves, paper, andpostal systems. Note that there may be multiple channels associated with the multiple layers of transmission, as described above.
6. Noise, in the form of secondary signals that obscure orconfuse the signal carried. Given Shannon's focus on telephone transmission, carriers, and reception, it should not be surprising that noise is restricted to noise that obscures or obliterates some portionof the signal within the channel. This is a fairly restrictive notion of noise, by current standards, and a somewhat misleading one. Today we have at least some media which are so noise free thatcompressed signals are constructed with an absolutely minimal amount information and little likelihood of signal loss. In the process, Shannon's solution to noise, redundancy, has been largely replacedby a minimally redundant solution: error detection and correction. Today we use noise more as a metaphor for problems associated with effective listening.
7. A receiver. In Shannon's conception,...