  The fluctuation relation, a milestone of modern thermodynamics, is only
established when a set of fundamental currents can be measured. Here we prove
that it also holds for systems with hidden transitions if observations are
carried ``at their own beat,'' that is, by stopping the experiment after a
fixed number of visible transitions, rather than the elapse of an external
clock time. This suggests that thermodynamic symmetries are more resistant to
the loss of information when described in the space of transitions.
