8 BELL SYSTEM TECHNICAL JOURNAL 



under the dial system are about the same in number as those made 

 by subscribers and operators under the manual system. 



Calls resulting in busy reports amount to 10 per cent. This is 

 something which is not directly under the control of the telephone 

 company since the subscriber determines the telephone facilities which 

 are provided. Records are kept, however, in both manual and dial 

 offices of the lines responsible for the greatest number of busy reports 

 and efforts are made to have the subscribers take additional facilities. 



Standards of transmission are applied to the design of the plant 

 to insure that transmission will be clear between the most remote 

 parts of the exchange area. This depends on the design of station 

 equipment, wire lines and switchboard equipment, and is expressed 

 in terms of the combined electric and acoustic efficiencies of the cir- 

 cuits from the mouth of the talker to the ear of the listener. This 

 overall efficiency is expressed in terms of the adjustment of a standard 

 reference circuit. The standards in use in the United States refer 

 to the maximum transmission loss permitted between any two sub- 

 scribers and vary in magnitude between equivalents of 18 decibels 

 and 22 decibels, depending on the circumstances of different cases. 



In order to meet these transmission standards the Bell Companies 

 have standard requirements regarding the efficiency of transmitters 

 and receivers and other station equipment, and these are made the 

 basis for engineering the wire plant. Transmission losses in switch- 

 boards are kept as low as practicable and within specified limits. 

 The wire plant for subscribers lines and trunks is designed to be within 

 the limits required for meeting the transmission standards. If under 

 special conditions it appears desirable to exceed these limits, this is 

 done only with the approval of responsible engineering authorities. 



To handle calls at the local switchboards there was in the Bell 

 System in 1928 an average operating force of about 122,000 young 

 women. In addition an average force of approximately 36,000 were 

 employed at the toll boards of the Bell System. This made a total 

 operating force of 158,000. In order to make up for losses and for 

 growth, 75,000 women were employed, and to select this number 

 approximately 300,000 applicants were interviewed. 



One of the important administrative problems is the scheduling 

 of the operating forces so that an adequate number may be available 

 in each central office throughout every period of the day. A method 

 has been worked out whereby all types of operating work are equated 

 to a common unit of measurements and the number of such units 

 that an operator should handle to give the best service most efficiently 

 has been determined. Frequent counts are maintained of the num- 



