2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/35883The transmission time of an electromagnetic signal in the vicinity of the earth is calculated to c-2 and contains an orbital Sagnac term. On earth, the synchronisation of the Barycentric Coordinate Time (TCB) can be realised by atomic clocks, but not the one of Geocentric Coordinate Time (TCG). The principle of equivalence is discussed.9 pages, Latex, no figure. Copies available at goy@axpba1.ba.infn.itGeneral Relativity and Quantum Cosmologytext