File:EB1911 Telegraph - Multiplex Working.jpg

English: The multiplex telegraphy system devised by Patrick B. Delany (which was adopted to a limited extent in Great Britain, but has now been entirely discarded) had for its object the working of a number of instruments simultaneously on one wire. The general principle of the arrangement of the apparatus is shown. Arms a and b, one at each station A and B, are connected to the line wire, and are made to rotate simultaneously over metallic segments, 1, 2, 3, 4, and 1′, 2′, 3′, 4′, at the two stations, so that when the arm a is on segment 1 at A, then b is on segment 1′ at B, and so on. At each station sets of telegraph apparatus are connected to the segments, so that when the arms are kept rotating the set connected to 1 becomes periodically connected to the set connected to 1′, the set connected to 2 to the set connected to 2′, and so on. In practice the number of segments actually employed is much greater than that indicated on the figure.