Figure 1
Information from the intrinsic perspective. Different channels constituted of wires carrying a physical signal with two states (for example, high or low voltage); the brackets pointing up represents the encoding of the symbols into the physical signal(s) and the brackets pointing down represent the decoding. (A) Extrinsic perspective: encoders and decoders can be designed to find the alphabet that maximizes information transmission (channel capacity), and this alphabet is shared by both sender and received. (B) Intrinsic perspective: has fixed encoders and decoders for sending and receiving information. The remaining panels depict three enclosures where your only interface with the environment is an input channel (top) connected to a screen and an output channel (bottom) connected to a keyboard. (C) a channel with one noiseless wire, conveying one bit that is encoded (decoded) into a symbol (a dot or a dash); (D, E) channels with eight wires each and an encoder (decoder) that converts the eight bits (a byte) into one out of 256 characters (or vice-versa). In (D), all eight wires are noiseless. In (E), the first wire is noiseless while the other seven wires are fully noisy (indicated by the lightning signs) so they rarely convey the original signal. In all cases the keyboard is connected to noiseless output wires (bottom) and has as many keys as possible input symbols. How should you rank the three enclosures with respect to the information you could relay?
