We show that for a large class of piecewise monotonic transformations on a
totally ordered, compact set one can construct conformal measures and obtai
n the exponential mixing rate for the associated equilibrium state. The met
hod is based on the study of the Perron-Frobenius operator. The conformal m
easure, the density of the invariant measure and the rate of mixing are ded
uced by using an appropriate Hilbert metric, without an compactness argumen
ts, even in the case of a countable to one transformation.