Features an electronic sentry to protect the operator and the patient from a malfunction… every time you step on the foot control it scans for problems… if one is found, the sentry automatically deactivates the unit. Soft tissues vary in electrical resistance, the deeper the cut the hight the load on the device. The SENSIMATIC 600SE has unique solid-state circuitry that acts like the automatic transmission in your car... if you need more power it delivers... automatically! No need to fiddle with dials in the middle of a produce