The MD4458-AAII mesh node has 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 in underground mining. In underground mining applications the inclined tunnel shaft requires two service radios each connected to 180 degree inclined panel antennas facing opposite directions of the mine shaft. Customers found that other products with a single AP inadequate - the single radio antenna could not be inclined.(MD 4458-AAII)
 
MD4458 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. The configuration below is: MD4458-AIII.    
 
Related Links: 

1. MD4000 Model Numbering Scheme lists variants of our product configurations (e.g.  MD4458-AIII).