Note 1: By "effective recorded spot dimension" is meant the largest center-to-center spacing between recorded spots, which gives minimum peak-to-peak variation of density of the recorded line.
Note 2: "X-dimension of recorded spot" implies that the facsimile equipment response to a constant density in the object (original) is a succession of discrete recorded spots.
Source: from Federal Standard 1037C and from MIL-STD-188