  Sleeping problems have become one of the major diseases all over the world.
To tackle this issue, the basic tool used by specialists is the Polysomnogram,
which is a collection of different signals recorded during sleep. After its
recording, the specialists have to score the different signals according to one
of the standard guidelines. This process is carried out manually, which can be
highly time-consuming and very prone to annotation errors. Therefore, over the
years, many approaches have been explored in an attempt to support the
specialists in this task. In this paper, an approach based on convolutional
neural networks is presented, where an in-depth comparison is performed in
order to determine the convenience of using more than one signal simultaneously
as input. Additionally, the models were also used as parts of an ensemble model
to check whether any useful information can be extracted from signal processing
a single signal at a time which the dual-signal model cannot identify. Tests
have been performed by using a well-known dataset called expanded sleep-EDF,
which is the most commonly used dataset as the benchmark for this problem. The
tests were carried out with a leave-one-out cross-validation over the patients,
which ensures that there is no possible contamination between training and
testing. The resulting proposal is a network smaller than previously published
ones, but which overcomes the results of any previous models on the same
dataset. The best result shows an accuracy of 92.67\% and a Cohen's Kappa value
over 0.84 compared to human experts.
