学术降重：HDB3码的全称是3阶高密度双极性码它是AMI码的一种改进型其目的是为了保持 AMI码的优点而克服其缺点使连0个数不超过3个HDB码保持了AMI码的优点同时还将连0码限制在3个以内这个规律可用来检错并有利于位定时信号的提取。HDB3码是应用最为广泛的码型A律 PCM 四次群以下的接口码型均为HDB3码μ律PCM四次群以下的接口码型使用扰乱处理后的AMI 码扰乱处理可以减少AMI码中连零的

Academic paraphrasing: HDB3 code stands for high-density bipolar 3rd order code, which is an improved version of AMI code. Its purpose is to maintain the advantages of AMI code while overcoming its limitations by limiting the number of consecutive zeros to no more than 3. HDB3 code retains the advantages of AMI code and is useful for error detection and extraction of timing signals. HDB3 code is the most widely used code type and is used for A-law PCM interface code types below 4th order group, while µ-law PCM interface code types below 4th order group use scrambled AMI code to reduce the number of consecutive zeros.