why bit errors accumulate?

[honhungoc]

As i know, in PCM transmission, noise does not accumulate due to regenerative process carried out at repeaters, however bit errors do accumulate.

Anyone please explain me why bit errors accumulate

Thank u

 

[A.Anand Srinivasan]

when regenerative process is carried the noise gets eliminated due to the inherent noise margin while it is not the case for bit error.... it just gets transmitted.... so it gets accumulated...