Scanner

A Scanner is a UNSC detective equipment seen being used by S. Hartley of Alpha Team in Part 2 of the Arms Race video trilogy.Halo Arms Race Part 2
The scanner appears to be used for displaying the location of a tracking signal. It is possible that it is used for other purposes, although none are shown. 
The scanner appears to contain a flat panel display and emits a beeping that gets faster the closer it is to the target.
==Sources==