Physical layer and Numerical transmissions物理层与数据传输 2

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Formats and Standard 2

• 多种协议 different protocols

Code NRZ (Non Return to Zero) 不归零码

Binary Séquence  10000101111

As picture showed below, after a +level, the votage inverted as a -level, rather than back to 0 level.

Code NRZI (Non Return to Zero Inverted)

NRZ-I编码中，编码后电平只有正负电平之分，没有零电平，是不归零编码。

Utilisation : Fast Ethernet (100BaseFX), FDDI

Principe : transition for a one bit and nothing for 0. 翻转代表0，不变代表1。

注：上图中第一个电压信号有错误，第一个应为负。

基带传输技术 Codage MLT3  （MLT3基带码是一种归零编码RZ）

Utilisation : Fast Ethernet (100BaseTX, 100BaseT4), ATM,

Principle: In this encoding, only 1  change the status signal. The coded 0 retaining the value previously transmitted. The one are encoded successively in three states: + V, 0 and-V.

1.如果下一比特是0，则输出值与前面的值相同；