Before revision: As such, slow communications technologies like mail and pneumatic tubes are excluded from the definition.Constitution and Convention of the International Telecommunication Union, Annex (Geneva, 1992) Many transmission media have been used for telecommunications throughout history, from smoke signals, beacons, semaphore telegraphs, signal flags, and optical heliographs to wires and empty space made to carry electromagnetic signals.
After revision: postalAs such, slow communications technologies like mail and pneumatic tubes are excluded from the definition.Constitution and Convention of the International Telecommunication Union, Annex (Geneva, 1992) Many transmission media have been used for telecommunications throughout history, from smoke signals, beacons, semaphore telegraphs, signal flags, and optical heliographs to wires and empty space made to carry electromagnetic signals.