198011 – Thomson – Application of Computers with Time Division Multiplex Systems

Time Division Multiplex (T.D.M.) systems have been used for many years by Railways and other Authorities for the transfer of digital information between two or more locations. The earliest use of T.D.M. systems was with telegraph communication and as costs have reduced they have been progressively introduced into other applications until to-day they are used to control toys.

A major factor 3×1 this change has been the adoption of digital computer techniques to the processing of the input and output data to and from the communications link.

In the following sections development and the use of computer based systems will be discussed.

The principles of Time Division Multiplex systems have been described in many papers presented before this institution*, with the general principles of operation being well covered in the paper by B.H. Grose entitled “Remote Control of Railway Signal Interlocking Equipment”.

Figure 1 outlines the basic principles. In operation the scanners are maintained in synchronism and each input is connected for a period of time to its associated output. For a two way system, the transmission system is shared for each direction of transmission.