[Milsurplus] Navigation System

[William Donzelli]

> That's a salient point, but there are mitigating (or at least anomalous) 
> factors that tend to mess up the orderly theory.

In addition, the order can be screwed up by the planning itself. When the
set is first envisioned by the military, sometimes the number and types of
assemblies are know, sometimes not. This is apparent in radar systems -
sometimes the planners spec the business end of the radar to be a combined
RT unit, and sometimes not. If not, the desicion to assign R, T or RT
numbers has to wait until the engineers get stuff worked out.

Sometimes one will see sets marked UNIT 1 OF AN/ABC-123, yet other times
R-987/ABC-123. The truth and reason probably lies in the lost notes and
minutes of many engineering meetings.

Things really get complicated when existing units are used for new
sets. When AN/ARN-7 was assigned, most of the engineering was done. In the
forementioned AN/MRC-20, the engineers did most of their work shopping out
of a directory..