By constructing the Lifeguard without the internal spring, the Safeguard is a great tool for rescue and rigging work. It will lock onto the rope with very little force giving you the confidence that once the position of the rope is set the device will not creep or slide.
This belay device does not operate like most auto-brake assist devices, and is not meant for lead climbing. It is for rigging and other types of rope access projects.
The Safegaurd (aka Lifeguard Black Edition) does not have a camming spring. Without this spring, the cam is always on, braking the rope. So any minute force from the climbers side of the rope, will keep the climber held at all times.
If you are looking for an auto-brake assist belay device for top roping and lead climbing, check out the Mad Rock Lifeguard instead.