An instant messaging application intelligently infers a user’s unavailability from one or more indicia which include the user’s electronic calendar. The light may be mounted in such a way as to transmit light through a rotatable collar on the power tool, through or through a member of a housing of the power tool, or from the moving end effector. The sensor 82 includes a sonic conduit 144 extending around a portion of a circumference of the rotor 68 of the valve assembly 46.