4.6.3. Coding (Coding)

Parameter Number: 0x1603

Description: The Coding parameter defines the coding scheme to be used by a digital line type.

Values:

• 7 = B8ZS - This is a modified AMI code that only applies to T-1 lines and is used to preserve one's density on the line. Whenever eight consecutive zeros occur on the line, they are replaced by an 8-bit string that violates the bipolar signaling. If the preceding pulse was positive, the polarity of the substituted eight bits is 000+-0-+. If the preceding pulse was negative, the polarity of the substituted eight bits is 000-+0+-.
• 8 = AMI - Alternate mark inversion is a bipolar signal conveying binary digits in which each successive 1 (mark) is of the opposite polarity. If the previous mark was a positive pulse, then the next mark will be a negative pulse. Spaces have an amplitude of zero (no pulse).
• 9 = HDB3 - High density bipolar three zero is a modified AMI code that only applies to E-1 and is used to preserve one's density on the line. Whenever four consecutive zeros appear, the four-zeros group is replaced with an HDB3 code. This could be either of two HDB3 codes, depending on whether there was an odd or even number of ones since the last bipolar violation. If an odd number of ones occurred, the substituted four bits are 000V, where V represents a bipolar violation. If an even number of ones occurred, the substituted four bits are P00V, where P represents a parity bit and V represents a bipolar violation.

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