  We propose a simple model of coupled heat and particle transport based on a
zero-dimensional classical deterministic dynamics which is reminiscent of a
railway switch whose action is only a function of the particle's energy. It is
shown that already in the minimal three-terminal model, where the second
terminal is considered as a probe with zero net particle and heat currents, one
can find extremely asymmetric Onsager matrices as a consequence of
time-reversal symmetry breaking of the model. This minimalistic transport model
provides a better understanding of thermoelectric heat engines in the presence
of time-reversal symmetry breaking.
