TIME DIVISION MULTIPLEX SYSTEMS 221 



methods with competing methods of superimposing channels. Other 

 aspects to be considered are the synchronization of transmitting and receiv- 

 ing switching processes, the effects of non-linearities in the line, and the 

 sensitivity of the system to external interference. It is thought, however, 

 that the severe restrictions imposed on phase and attenuation characteristics 

 when economy of band width is required form the weakest feature of the 

 method and will in many cases provide the primary criterion for judging 

 its availability in the solution of particular problems. Conversely, if the 

 crosstalk requirements of the system are sufficiently mild to enable the 

 transmission problem to be solved, the other problems also become relatively 

 simplified. 



Further References 



A. M. Nicolson, U. S. Patents, 1,962,610; 2,021,743; 1,951,524; 1,956,397; 2,007,809. 

 Callahan, Mathes, and Kahn, "Time Division Multiplex in Radio-Telegraphic Practice," 



Proc. I. R. E., 26 (1938), 1, pp. 55-74. 

 H. Raabe, "Untersuchungen an der wechselzeitigen Mehrfachiibertragung (Multiplex- 



iibertragung)," E. N. T., 16 (1939), 8, pp. 213-228. 



