Published online by Cambridge University Press: 22 April 2019
We study continuous countably (strictly) monotone maps defined on a tame graph, i.e. a special Peano continuum for which the set containing branch points and end points has countable closure. In our investigation we confine ourselves to the countable Markov case. We show a necessary and sufficient condition under which a locally eventually onto, countably Markov map   $f$  of a tame graph
 $f$  of a tame graph   $G$  is conjugate to a map
 $G$  is conjugate to a map   $g$  of constant slope. In particular, we show that in the case of a Markov map
 $g$  of constant slope. In particular, we show that in the case of a Markov map   $f$  that corresponds to a recurrent transition matrix, the condition is satisfied for a constant slope
 $f$  that corresponds to a recurrent transition matrix, the condition is satisfied for a constant slope   $e^{h_{\text{top}}(f)}$ , where
 $e^{h_{\text{top}}(f)}$ , where   $h_{\text{top}}(f)$  is the topological entropy of
 $h_{\text{top}}(f)$  is the topological entropy of   $f$ . Moreover, we show that in our class the topological entropy
 $f$ . Moreover, we show that in our class the topological entropy   $h_{\text{top}}(f)$  is achievable through horseshoes of the map
 $h_{\text{top}}(f)$  is achievable through horseshoes of the map   $f$ .
 $f$ .