Transcriber's Notes.
Spelling variants where it wasn't possible to determine the author's intent were left as is. These include: "clockwork" and "clock-work;" "doorkeeper" and "door-keeper;" "interrelation" and "inter-relation;" "multicyclic" and "multi-cyclic;" "redesign" and "re-design," along with derivatives.
Added closing double quote in Steinmetz entry in list of authorities: "Theoretical Elements of Electrical Engineering."
Changed "switch-hook" to "switch hook" on page 88: "the subscriber's switch hook."
Page 107 says there is room for 300 banks of 100 multiple jacks, but then says this allows for 3,000 multiple jacks in all, rather than 30,000. Based on the figure, 300 banks should be 30 banks, which would correct the arithmetic. However, I did not change this.
Changed "bi-paths" to "by-paths" on page 185: "circuits or by-paths."
Changed "appararus" to "apparatus" on page 209: "The sectional apparatus."
Changed "two number" to "two-number" on page 312: "the two-number calls are ticketed."
On page 333, a paragraph begins with "It has been only within the past three few." Perhaps the author meant "It has been only within the past three years" or "It has been only within the past few years." But since I didn't know, I left is as is.
Changed "them ain" to "the main" on page 333: "on the main line."
Changed "weatherproof" to "weather-proof" on page 357: "iron weather-proof sets."
Changed "interoffice" to "inter-office" three times on page 364, to match the spelling in the body of the document: "meant by inter-office trunking;" "inter-office connection system;" "of the inter-office connection."
Changed "break-down" to "breakdown" on page 367: "provision against breakdown."
Changed "way-station" to "waystation" twice on page 372: "with a waystation set;" and "a waystation on a block wire."
Changed "way stations" to "waystations" on page 375, in the entry for Long-distance switching.
Each page of the Index repeated this text: "Note.—For page numbers see foot of pages." They were removed.