SDS Drills generally come with 2 settings, some come with 3. See the below for a detailed explanation of each:
This is like you’d expect an ordinary drill to work, although the maximum speed tends to be a bit slower (typically they’ll be under 1500 RPM) although the torque will be higher. In a similar vein to a diesel car.
Drill and hammer
This is what SDS drills are primarily designed for. With their improved hammer drill action. It’s strange that despite the fact that SDS drills perform better than standard drills they do tend to be quieter.
Hammer only, no rotation
Not all models have this setting. It’s often called “roto-stop”. By fitting special bits to the drill, such as chisel bits, you can greatly expand the range of jobs you can perform with the drill, like using it as a mini concrete breaker.
A common use of the hammer-only mode is to chase out cable runs or for cutting out sockets in walls. It really can be worth paying a little bit extra to get an SDS that comes with a hammer-only setting.