Digital transmission is much "cleaner" than analog because instead of being simply amplified (along with any noise and distortion), the digital signal is regenerated. It is "asked" a simple question: Is this signal a "one" or a "zero"?

When a distorted digital signal arrives at the input of a regenerative repeater, the repeater examines the signal during each bit position. If the input signal exceeds a designed threshold level, the repeater generates a new pulse. If the input signal does not exceed the threshold level, no pulse is generated.

In this manner, the digital signal is re-generated (rather than amplified) at each repeater, thereby eliminating the effects of transmission impairment.