A spike generator which produces a spike whenever the input exceeds a given threshold.
After generating a spike, no spike can be produced for a period refractoryPeriod. If the input is continuously above threshold, then a series of spikes will be produced at this interval.
Typically, when used with an integrator compartment the spike output will be connected to the reset port of the compartment, or to a response function or the compartment will include membrane channels which generate a spike waveform. (or any combination of the above).