  We present an algorithm for active learning of deterministic timed automata
with a single clock. The algorithm is within the framework of Angluin's $L^*$
algorithm and inspired by existing work on the active learning of symbolic
automata. Due to the need of guessing for each transition whether it resets the
clock, the algorithm is of exponential complexity in the size of the learned
automata. Before presenting this algorithm, we propose a simpler version where
the teacher is assumed to be smart in the sense of being able to provide the
reset information. We show that this simpler setting yields a polynomial
complexity of the learning process. Both of the algorithms are implemented and
evaluated on a collection of randomly generated examples. We furthermore
demonstrate the simpler algorithm on the functional specification of the TCP
protocol.
