  We compute the current voltage characteristic of a chain of identical
Josephson circuits characterized by a large ratio of Josephson to charging
energy that are envisioned as the implementation of topologically protected
qubits. We show that in the limit of small coupling to the environment it
exhibits a non-monotonous behavior with a maximum voltage followed by a
parametrically large region where $V\propto 1/I$. We argue that its
experimental measurement provides a direct probe of the amplitude of the
quantum transitions in constituting Josephson circuits and thus allows their
full characterization.
