| Each letter in the word is represented by different | | | | most of the transmission channels in spite of the fact |
| signal amplitude using thirty two scale order. If we do | | | | that the noise present in most channels is never |
| so information flow speed gets greatly increased as | | | | perfectly random. It is found that the limiting channel |
| per Hartley law. Since now each letter is represented | | | | speed for a typical telephone channel is about thirty |
| by one symbol instead of five. But in such a case | | | | three kilo bits per second. How ever speeds used in |
| noise will cause numerous error making the system | | | | practice over such channels do not normally exceed |
| useless extremely large transmitting power is used. | | | | eleven kilo bits per second. Doubling the speed the |
| This fact may be established on comparing the power | | | | bandwidth of a noise limited channel will double its |
| requirements for the binary coding system and any | | | | capacity would amount to misinterpretation. Actually |
| N-level system under the same noise conditions. For a | | | | the capacity gets increased by only eighty percent |
| given transmission and coding system there results are | | | | depending upon signal to noise ratio. Thus we see that |
| threshold noise levels below which practically no errors | | | | there exists possibility of trading bandwidth for signal to |
| occur due to noise. Using binary code noise has to | | | | noise ratio. It may also be noted that a low channel |
| compete with the full power of the transmitter to | | | | capacity does not mean that the desired amount of |
| cause any serious error. It is found that in a practical | | | | information can not be seen over a given channel. It |
| channel, signal to noise ratio of thirty decibel ensures | | | | simply means sending this amount of information takes |
| almost error free reception. This thirty decibel ratio | | | | longer time. Lastly it may be seen that the |
| implies that noise power be one by thousand of signal | | | | Shannon-Hartley theorem represents a fundamental |
| power or root mean square noise voltage be one by | | | | limitation. Any attempt to exceed the Shannon limit |
| thirty one of root mean square signal voltage. | | | | would result in unacceptable error rate. In good quality |
| The transmitted power is required to rise tremendously | | | | transmission system maximum acceptable error ratio |
| if a desired high signal to noise power ratio is to be | | | | is one in 1000000. All the messages sent though the |
| maintained on increasing signaling speed that is on | | | | noise limited channel are unpredictable or random. |
| increasing the number of coding levels. | | | | Tymon Hytem has worked in the electronics feild for |
| Shannon-Hartley theorem gives the maximum signaling | | | | the past 15 years. He enjoys helping people decide on |
| speed in a channel in which the noise is purely random. | | | | electronic gadgets from telephones to XM Radio and |
| This theorem may be used as a very good | | | | choosing the perfect XM Satellite Radio system for |
| approximation for the ultimate channel capacity of | | | | their needs. |