The Bell System Technical Journal 



Vol. XVI January, 1937 No. 1 



A Million-Cycle Telephone System * 



By M. E. STRIEBY 



ABOUT two years ago a new wide-band system for multi-channel 

 telephone transmission over coaxial cables was described.^ An 

 experimental system has now been installed between New York and 

 Philadelphia. The various tests and trials which are planned for this 

 system have not been carried far enough to justify a formal technical 

 paper. Meanwhile, the considerable interest that has been aroused 

 in the system has led to this brief statement of its principal features and 

 its general technical performance as so far measured. 



The coaxial cable itself has been installed between the long distance 

 telephone buildings in New York and Philadelphia, a distance of 

 94.5 miles. It has been equipped with repeaters, at intervals of about 

 10 miles, capable of handling a frequency band of about 1,000,000 

 cycles. 



This million-cycle system is designed to handle 240 simultaneous 

 two-way telephone conversations. Only a part of the terminal 

 apparatus has been installed, sufficient in this case to enable adequate 

 tests to be made of the performance of the entire system. A general 

 view of the New York terminal is shown in Fig. 2. Some preliminary 

 test conversations have been held over the system, both in its normal 

 arrangement for providing New York- Philadelphia circuits, and with 

 certain special arrangements whereby the circuit is looped back and 

 forth many times to provide an approximate equivalent of a very long 

 cable circuit. The performance has been up to expectations, and no 

 important technical difficulties have arisen to cast doubt upon the 

 future usefulness of such systems. Much work remains to be done, 

 however, before coaxial systems suitable for general commercial 

 service can be produced. 



The Coaxial Cable 



Figure 1 shows a photograph of the particular cable used in this 

 installation. It contains two coaxial units, each having a 0.265-inch 

 inside diameter, together with four pairs of 19-gauge paper insulated 

 wires, the whole enclosed in a lead sheath of 7/8-inch outside diameter. 



* Published in Electrical Engineering for January, 1937. 



^ "Systems for Wide-Band Transmission Over Coaxial Lines" by L. Espenschied 

 and M. E. Strieby, Bell Sys. Tech. Jour., October, 1934; Elec. Engg. {A. I. E. E. 

 Transactions), Vol. 53, 1934, pages 1371-80. 



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