DIALING BEHAVIOR OF SUBSCRIBERS 427 



line busies were used instead of all-trunks-busy signals because it would have 

 taken too long to obtain sufficient observations, because it is undesirable to 

 artificially degrade the service in order to obtain sufficient observations and 

 because it is assumed that the average subscriber does not recognize the 

 difference between a busy and overflow signal. It is considered that the 

 data, while collected for busy signals, accurately represent the situation 

 with regard to overflow signals. 



Beginning on December 22, 1943 and ending on February 29, 1944, a 

 special record of 1,107 subscriber-dialed calls, where line busies were ob- 

 served, was taken at the three New York City service observation bureaus. 

 Up to a point, regular service observation practices were followed and the 

 regular service observing data concerning the calls were entered on the 

 service-observang records. The data concerning the line busies were entered 

 on a special form. This form is shown below. Instructions for the observers 

 accompanied these forms; these instructions follow the form. 



Form S.O. 171 



Special Records — Busy Calls 



Calling No Date 



Enter in space under attempt number, the cumulative seconds from the start of the 

 original attempt to the start of the attempt indicated. In addition for the last attempt 

 show disposition. 



Disposition of the call 



Data for attempts over 20 should be entered on the reverse side. 



Special service observing form used to collect data concerning the dialing behavior of 

 subscribers upon encountering a busy. 



Instructions A pplying to the Use of Form S.O. 171 



These instructions apply to the use of Form S.O. 171 which has been de- 

 veloped in connection with a study of the behavior of customers upon en- 

 countering a busy signal. 



This study will not include observations originating on P.B.X. trunks or 

 on coin lines. On all other calls encountering a busy signal or an overflow 

 signal the observer will hold the line in the observing position until one of 

 the following conditions occurs: 



(1) Call is disposed of by reaching the desired number. — Code OK 



