Time Division Multiplex Systems

THE idea of transmitting and receiving independent signals over a common line by means of synchronized switches at the terminals is quite old and has been used in multiplex telegraphy for many years. In general if N signal channels are to be provided over one line, the switching cycle includes N equal time intervals, one of which is allotted to each channel. Each channel is connected to the line throughout a part of its particular time interval and is disconnected throughout the remainder of the cycle. Absence of interference between the channels depends upon the fact that the channels are connected to the line throughout mutually exclusive time intervals. It is thus possible to avoid the use of channel band filters such as are necessary in carrier systems employing frequency as the basis of separation.