Fig. 2.

The standard deep RNN architecture. The simplified RNN architecture is shown in the box on the left. The box on the right shows the architecture unfolded in a form of time-series data [..., t - 1, t, t + 1,...]. Connections exist in the recurrent hidden layers; the input information of hidden layer “t” contains the output information of hidden layer “t+1”, and the sequential relationships over time are connected by horizontal lines