National Geographic : 1919 Mar
Multiplexing the Telephone Marvel has followed marvel since Alex ander Graham Bell invented his first simple telephone, the forerunner of the millions in use today. In these last four decades thousands of Bell engineers have developed a system of telephonic communication, so highly per fected, that the same crude instrument which at the beginning could hardly carry speech from one room to another can now actually be heard across the continent. This is be cause of the many inventions and dis coveries which have been applied to inter vening switchboard, circuits and other trans mitting mechanism. The vision of the engineers has foreseen requirements for increased communication, and step by step the structure of the art has been advanced-each advance utilizing all previous accomplishments. No one step in advance, since the original invention, is of greater importance, perhaps, than that which has provided the multiplex system by which five telephone conversa tions are carried on today simultaneously over one toll line circuit or, by which forty telegraphic messages can be sent over the one pair of wires. As in a composite photograph the pictures are combined, so the several voice waves mingle on the cir cuit to be again separated for their various destinations. By this wonderful development the Bell System obtains for the public a multiplied usefulness from its long distance plant and can more speedily and completely meet the needs of a nation of telephone users. AMERICAN TELEPHONE AND TELEGRAPH COMPANY AND ASSOCIATED COMPANIES TM 1) ... One roizcy One System Universal Service "Mention The Geographic-It identifies you"