# understanding discrete wavelets

I was reading section 4.3.3 from chapter 4 of "A Wavelet Tour of Signal Processing",

"...Let $\bar{f}(t)$ be a continuous time signal defined over $[0,1]$. Let $f[n]$ be the discrete signal obtained by a low-pass filtering of $\bar{f}$ and uniform sampling at intervals $N^{-1}$.

Its discrete wavelet transform can only be calculated at scales $N^{-1}<s<1$,..."

Why is this so? I don't understand