Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for allocating probing responsibilities between a primary sensor and a secondary sensor. In one aspect, a method includes determining a first probe type, the first probe type being the probe type of the highest priority information probe for which a reply from the host device was received at the primary sensor, determining a second probe type, the second probe type being the probe type of the highest priority information probe for which a reply from the host device was received at the secondary sensor, determining whether the second probe type is prioritized higher than the first probe type, and allocating probing responsibilities between the primary sensor and the second sensor based on the prioritization of the first probe type and the second probe type.