Einstein synchronisation

Einstein synchronisation (or Poincaré–Einstein synchronisation) is a convention for synchronising clocks at different places by means of signal exchanges. This synchronisation method was used by telegraphers in the middle 19th century,^{[citation needed]} but was popularized by Henri Poincaré and Albert Einstein, who applied it to light signals and recognized its fundamental role in relativity theory. Its principal value is for clocks within a single inertial frame.