- The information source selects a desired message out of a set of possible messages.
- The transmitter changes the message into a signal that is sent over the communication channel to the receiver.
- The receiver is a sort of inverse transmitter, changing the transmitted signal back into a message, and interpreting this message.
- This message is then sent to the destination. The destination may be another receiver (i.e., the message is passed on to someone else), or the message may rest with the initial receiver, and the transmission is achieved.
- In the process of transmitting a message, certain information that was not intended by the information source is unavoidably added to the signal (or message). This "noise" can be internal (i.e., coming from the receiver's own knowledge, attitudes, or beliefs) or external (i.e., coming from other sources). Such internal or external "noise" can either strengthen the intended effect of a message (if the information confirms the message), or weaken the intended effect (if the information in the "noise" contradicts the original message).
Shannon, C. E. A Mathematical Theory of Communication The Bell System Technical Journal, Vol. 27, pp. 379-423, 623-656, July, October, 1948.