General Order 64-A
Section IV
Strength Requirements For All Classes Of Lines
42 Grades of Construction
The grades mentioned herein are established on the basis of the relative hazards existing. Grades “A,” “B” and “C” apply to supply or communication circuits, while Grade “F” applies to communication circuits under normal conditions.
For all classes of lines, the relative order of grades is “A,” “B,” “C” and “F,” grade “A” being the highest. Table 3 following designates the grade of construction to be used in the erection and maintenance of supply and communication circuits:
Table 3 Grades of Construction