  Suppose $P\subseteq \mathbb{N}$ and let $(\Sigma_P,\,\sigma_P)$ be the space
of a spacing shift. We show that if entropy $h_{\sigma_P}=0$ then
$(\Sigma_P,\,\sigma_P)$ is proximal. Also $h_{\sigma_P}=0$ if and only if
$P=\mathbb N\setminus E$ where $E$ is an intersective set. Moreover, we show
that
  $h_{\sigma_P}>0$ implies that $P$ is a $\Delta^*$ set; and by giving a class
of examples, we show that this is not a sufficient condition. Then there is
enough results to solve question 5 given in [J. Banks et al., \textit{Dynamics
of Spacing Shifts}, Discrete Contin. Dyn. Syst., to appear.].
