Response time is the time required for a dimmer to turn on a load from off to its level, when commanded to do so via a DMX512 level change. Thyristor dimmers are typically very fast (20-50 milliseconds), while sine wave and IGBT dimmers may be slower, due to the fact that they must limit inrush current from a cold lamp filament to protect the transistor power handling devices in the dimmer. Inrush current from a cold filament may be 20X normal lamp operating current. Response time should never be confused with rise time, which is the turn-on (or turn-off in a reverse phase-control dimmer) time in each half cycle of the power devices in a phase-control thyristor or IGBT dimmer. Rise times are measured in microseconds, while response time is typically measured in milliseconds.