I am currently studying encoding techniques. The scrambling technique HDB3 is introduced as follows:
- High-Density Bipolar-3 Zeros
- Based on bipolar-AMI
- String of four zeros is replaced with sequences containing one or two pulses.
- A sequence of four consecutive zeros is encoded using a special 'violation' bit. This bit has the same polarity as the last 1-bit that was sent using the AMI encoding rule.
- The violation bit alternates between + and - pulses for every consecutive group of four zeros.
And the following example is given:
I don't understand the even/odd stuff. What does the "parity of the +/- bits since previous V" mean, and how does one ascertain the even/odd values (that is, how can we tell if it's supposed to be "even" or "odd", as shown by the arrows) as in the example?