The Western Union Varioplex telegraph system

The Varioplex system is a type of automatic telegraph system in which a large number of individual variable-traffic-capacity lanes of communication are provided by means of a single trunk circuit. A Varioplex circuit between two distant cities may be arranged to provide for any number up to 40 subchannel connections. A firm with offices in these cities leasing one of these sub-channels is thereby provided with a direct and private circuit between the two offices. Each office is furnished with 2 teleprinters, one for sending and the other for receiving and communication can be carried on in either or in both directions at the same time. Typical installations are described, with particulars of the central office equipment and its operation. More than 50 Varioplex circuits, comprising over 500 sub-channels, form a network which extends over the entire U.S.A. and further expansion is probable after the war.