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Alternate Mark Inversion Code

Tool to decode/encode with AMI. The (bipolar) Alternate Mark Inversion is a line coding for binary signal with a 3-level system representing logical ones by an impulsion with alternative positive or negative polarity.

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Alternate Mark Inversion Code -

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# Alternate Mark Inversion Code

## AMI Line Encoder

### How to encrypt using Alternate Mark Inversion?

The AMI code replaces each logical 1 by a polarity inversion noted with + (plus) and - (minus). Some notations use +1 and -1 (instead of + and -) but the vast majority of the time, the 1 is ignored as, it is implied.

For each logical 0 (zero), nothing to do: 0 is coded, and for each logical 1 (one), a polarity impulsion is coded: alternatively (+ or -), beginning by +.

Example: The binary/logical signal 101 is coded +0-:
1 is coded +
0 remains 0
1 becomes - (polarity changed)

### How to decrypt Alternate Mark Inversion line code

AMI code decryption process replaces each + or - by a logical 1, the rest (the zeros) is 0.

Example: +0- is decoded 101

### How to recognize an Alternate Mark Inversion coded signal?

The signal is bipolair (positive and negative) and has three levels, that can be coded with 3 distinct characters, generally +, - and 0. Sometimes the 1 is still written after + and -.

There is never two consecutive upper ++ or lower -- levels when coding.

### How to begin with a negative polarity?

A signal beginning with a negative polarity starts with a 1 at the beginning of the plain signal and causes a suppression of the first + of the coded signal.

### When Alternate Mark Inversion was invented?

In the 60's, after the T1 (T-carrier level 1).

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