The First Order Hold block is a mathematical model of the practical reconstruction of sampled signals that could be done by a conventional digital-to-analog converter (DAC) and an analog circuit called an integrator. For the FOH, the signal is reconstructed as a piecewise linear approximation to the original signal that was sampled. We can test the DAC with the Colink model shown in the below figure The Sine block is configured to a frequency of 10rad/sec and an amplitude of 1. The First Order Hold block Sample time is set to 0.1. Set solver type to Fixed-Step, discrete (no continuous states), and let End time be 1.
Figure 1 colink model
Figure 2 A result from scope