This model illustrates the use of SR within DE. The SR director executes a "tick" of the inside model when it gets either a "start" event or a "tick" event. Since it is provided with a "tick" event once per second, it will tick at least that often. Given an input integer on the "start" input, the SR submodel will count down from that integer until either it reaches zero or it receives another input integer. Note that the Default actor inside the SR model performs a nondeterministic merge, as in Signal, but with the nondeterminism resolved by the environment model, which is the DE top-level model.
See also the untimed version of this model.