Unipolar encoding

This line code isn't very popular because it will create a significant DC-value. It works by setting a +1 rectangular pulse to binary 1, and a flat line to represent a binary 0.

You can reduce the DC by one-half by using return-to-zero (this line code method works with both NRZ - nonreturn to zero, or RZ - return to zero). With a half duty cycle each rectangular pulse is only at +1 V for half a period. This is ideal if you expect to recieve 1 symbol much more often than the other and you have power considerations (i.e.- you are only energizing the channel for half a period when you come across a symbol you occassionally hit).

~s. henry