An Integrated PCM Network

Until recent years, exchanges of information over long distances were made by various means which can be classified in the order of the volume of information to be transmitted: 1) Written documents. 2) Speech in the form of analog signals. 3) Coded means (mainly telegraph and telex). 4) Analog means (television, facsimile). The last three fall within the field of electronics. This paper describes a transmission and switching method using digital signals which is able to transmit coded or analog information including speech. The method of transmitting information is a digital switching and transmission network using cable or radio circuits and, as a type of modulation for analog signals, Pulse Code Modulation (PCM). Such a system, presently in the course of development, is herein described.