Regulator (index)

In its first sense, the regulator is a small index pivoted on the balance cock that changes how much of the hairspring is free to work. The published European patent application EP 3 502 788 A1, Standalone device for adjusting the active length of a hairspring (application EP 17208988, filed 20 December 2017, published 26 June 2019), describes exactly this arrangement: "a regulator mounted on a plate with a cock", with the balance spring stud holder "being pivotally mounted on the cock", and with "a pivot arm and device for changing the active length of the balance spring by pivoting the regulator". Shortening the active length makes the balance swing faster; lengthening it slows the watch down.

In its second sense the word has nothing to do with that part. A regulator is a precision clock, and the name also attaches to its dial layout. Royal Museums Greenwich catalogues "An eight-day oak astronomical longcase regulator by George Graham, London, No. 675, circa 1725, Known as 'Graham No.2'", whose twelve-inch silvered dial carries "an outer minute circle" with "a recessed hour subsidiary dial" and "a subsidiary seconds dial with observatory marks," the separated indications that the phrase regulator dial still describes on watches today.

The two senses are unrelated in function, and this Codex does not pretend the word has one meaning: one is a rate-adjusting part inside a movement, the other a kind of clock and the dial arrangement named after it. Neither is covered by a standard that could be read here. The Federation of the Swiss Watch Industry's published list of available NIHS norms contains no entry for the raquette, the French name for the index.