Laws of Cricket 1947 Code - Law 45
Before the toss for innings, the Umpires shall acquaint themselves with any special regulations, and shall agree with both Captains on any other conditions affecting the conduct of the match; shall satisfy themselves that the wickets are properly pitched; and shall agree between themselves on the watch or clock to be followed during play.
Notes on Law 45
1. Apart from "Special Regulations" (see Law 10, Note 1), other conditions of play within the framework of the Laws are frequently necessary, e.g., Hours of play, Intervals, etc.
2. The captains are entitled to know which clock or watch will be followed during play.
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