If you turn a line off for an amount of time equal to what the repeater is set to, the repeater feeding out of the line won't turn off. example: You have a redstone line wich is powered by default and a repeater set to two feeding out of it. If you turn the line off for two ticks and then on again, the repeater won't turn off at all

(NOT TESTED IN SNAPSHOT 13w07a OR LOWER)

picture 1: attach a repeater line like this to the contraption on the 2. picture so you can easily see the signal passing through if there is one

picture 2: a NOT gate signal shortener (repeater set to two.