Abstracts of Bell System Technical Papers 



Not Appearing in this Journal 



Voice- Frequency Carrier Telegraph System for Cables.^ H. P. 

 Hamilton, H. Nvgiisx. M. B. I.oxr. ami \V. P. Puki.is. Carrier 

 telegraph systems usinij frequencies above the voire range have been 

 in use for a number of years on open-wire lines. These systems, 

 however, are not suitable for long toll cable operation because cable 

 circuits greatly attenuate currents of high fretjuencies. The system 

 described in this paper uses frequencies in the voice range and is 

 specially adaptetl for operation on long four-wire cable circuits ten 

 or more telegraph circuits being obtainable from one four-wire circuit. 

 The siime carrier frecjuencies are used in both directions and are 

 spaceil 170 cycles apart. The carrier currents are supplied at each 

 terminal station by means of a single multi-frequency generator. 



Metallic Polar-Duplex Telegraph System for Long Small-Gage Cables.- 

 John H. Bi;ll, R. B. Sh.\N( k, and D. E. Br.wson. In connection 

 with carrying out the toll-cable program of the Bell System, a metallic- 

 circuit polar-duplex telegraph system was developed. The metallic- 

 return type of circuit lends itself readily to the cable conditions, its 

 freedom from interference allowing the use of low potentials and 

 currents so that the telegraph may be superposed on tele[)hone cir- 

 cuits. The new system represents an unusual refinement in direct 

 current telegraph circuits, the operating current being of the same 

 order of magnitude as that of the telephone circuits on which the 

 telegraph is superposed. 



The following are some of the outstanding features of the present 

 system. Sensitive relays with closely balanced windings are employed 

 in the metallic circuit, and "vibrating circuits" are provided for 

 minimizing distortion of signals. Repeaters are usually spaced 

 about 100 miles apart. Thirty-four-volt line batteries are used and 

 the line current is four or five milli-amperes on representative circuits. 

 Superposition is accomplished by the compositing method which 

 depends upon frequency discrimination, the telegraph occup\ing the 

 frequency range below that of the telephone. New local-circuit 

 arrangements have l)een designed, employing polar relays for repeti- 

 tion of the signals; these arrangements are suitable for use in making 

 up circuits in combination with carrier-current and ground-return 

 polar-duplex telegraph sections. New forms of mounting are em- 



' Journal A. I. E. E.. Vol. 44, p. 213, 1925. 



- Presented at the mid-winter convention of the .A. I. E. E., Feb., 1025. 



