internal noise in repeating system

the types of transmission systems which today are available for long distance transmission of large numbers of telephone circuits are those for coaxial cables and radio links. the number of circuits is increased in both cases in step with development in technique. radio links have for several years been able to transmit 600 telephone circuits per system. and are now being designed for 960 circuits. the capacity of the coaxial cable systems is now being increased from 960 to 10800 circuits per system. parallel with this increasing of capacity the problems as cross-talk and interference in this systems become more important. the problem of cross-talk between different systems on the same route can be overcome nowadays using relatively simple means. the main problem in both cases is the interference which arises within systems at the many points of amplification. interference ocurs there just as inevitably as friction in a machine and it is a difficult technical problem to design equipment in such a way that high transmission quality is obtained. the types of interference which accur most often are «babale» and «noise»thermal noise and itermodulation noise. in this article emphasis has been placed on the noise specially intermo, dulation noise and its relation with number of channels and repeaters in the system. at the end for practical using of what is written in this article and also for using c. c. i. t. t. recommendations about noise a repeated line is designed for open-wire, as an example.