158 BELL SYSTEM TECHNICAL JOURNAL 



and high-voltage capacitor. At the subscriber's location the signal is taken 

 off by similar means and led by separate wires to the subscriber premises, 

 where it is reconverted to voice frequency by means of a subscriber terminal. 

 A signal transmitted from the subscriber to the central office goes through 

 similar conversions. 



The usual number of parties per two-way channel may be assigned ac- 

 cording to local custom, and divided-code or full-code ringing is provided. 

 Equipment is available for live two-way channels over a single-power line 

 employing frequencies in the range 150 to 425 kilocycles. A sixth channel 

 has been discontinued because of radio interference. 



A description is given of the manner in which the power line should be 

 treated in order to reduce reflection effects. The power line treatment does 

 not affect its capabilities in regard to power transmission. 



Application of Rural Carrier Telephone System} E. H. B. Bartelink, 

 L. E. Cook, F. A. Cowan,* and G. R. Messmer. This paper deals with 

 the application of a carrier system developed primarily for providing rural 

 telephone service over power distribution circuits in areas where this means 

 of extending telephone service may be more attractive than other avail- 

 able methods. The modifications required in the power circuits to permit 

 carrier frequency transmission are described, including the effect of these 

 modifications on the operation of the power system. Construction fea- 

 tures also are discussed. The use of the rural carrier telephone system over 

 open wire telephone pairs is discussed briefly. 



An Improved Cable Carrier System} H. S. Black, F. A. Brooks, A. J. 

 WiER and I. G. Wilson. A new 12-channel cable carrier system is described 

 which is suitable for transcontinental communications. Important fea- 

 tures are negative feedback amplifiers of improved design, new arrangements 

 for accurate equalization of the cable loss, and automatic thermistor regu- 

 lators which continuously control the transmission of each system. 



Joint Use of Pole Lines for Rural Power and Telephone Services.^ J. W. 

 Campbell,* L. W. Hill, L. M. Moore, and H. J. Scholz. The use of 

 poles to carry both power and communication circuits is not new, having 

 been employed before 1890. There are today more than 6,000,000 poles 

 used jointly by power and telephone organizations in the United States. 

 The great bulk of these poles are located in urban areas where the voltages of 

 the power circuits concerned are generally less than 5,000 volts and the 

 span lengths between poles generally do not exceed about 150 feet. 



As power and telephone lines were extended into rural territory, new 



' Trans. A. /. E. E., vol. 66, 1947 (pi). 511-517). 

 '' Trans. A.L E. E., vol. 66, 1947 (pp. 741-746). 

 Trans. A. /. E. E., vol. 66, 1947 (pp. 519-524). 

 * Of Bell Tel. Labs. 



