The Signal compilation process is based on a formal analysis called clock calculus .I t constructively determines if a specification is endochronous by synthesizing a sequential control structure. The analysis applies to relations over clocks inferred from specifications and encoded into boolean equations. This paper first gives an overview of requisite fundamental notions related to clocks (control in data-flow specifications, link with operational semantics, boolean encoding) then uses this lighting to present technical aspects of the calculus [1,2].