MD4458-AAII mesh nodes have two access points which means it provides twice the AP radio power. Two 180-degree sector antennas may be used on each of the AP radios to cover a larger radius than a single omni-directional antenna.  Sometimes the clients can be distributed in separate directions from the mesh node; the use of sectored or directional antennas on the MD4458-AAII can cover such distributions - with each AP radio being on a different 802.11b/g channel.

MD4458_AAII is used in underground coal mining tunnels. Tthe inclined tunnel shaft requires two service radios each connected to 180 degree inclined panel antennas facing opposite directions of the mine shaft.
 

MD4458_AIII as an Edge Node with 3 AP radios. If the mesh node does not have any child nodes, then its downlink radio goes unused. This occurs with isolated nodes or with nodes positioned at the edge of a mesh. For edge nodes with high client density, a third AP radio replaces the (unused) downlink radio provides three dedicated Access Point radios. See green boxes, above..