IL4TING TILiNSMISSION PERFORMANCE 125 



accidental irregularities in circuit conditions such as interruptions and 

 cutoffs, but from the standpoint of transmission design, attention can 

 be concentrated on the results obtained when the circuit is in normal 

 operating condition. Since failures to understand and exertion of 

 effort are experienced also in direct conversations, their occurrence in 

 telephone conversations obviously cannot be entirely ascribed to the 

 functioning of the circuit. Variations in these factors for different 

 types of circuits can, however, be used as a measure of the effect of the 

 differences in the transmission characteristics of these circuits. 



The repetitions required in a conversation can be noted but a deter- 

 mination of the effort factor presents difficulties. There is undoubtedly 

 the tendency in carrying on conversations, as in other activities, to 

 exert no more effort than is necessary to obtain what the participants 

 consider to be satisfactory results. This effort, however, will in 

 general be increased as the difficulty of conversing becomes greater 

 and so bears a relation to the increase in repetitions. Also, it is prob- 

 able that two dissimilar circuits which cause the same rate of repeti- 

 tions when used for the same service, will, on the average, call for the 

 same amount of effort by their users. 



In line with this, the rate of occurrence of repetitions requested by 

 the users of a particular telephone circuit in carrying on their regular 

 telephone conversations can be used as a direct measure of the service 

 performance of the circuit. By determining the repetition rate for a 

 large enough number of different people at the two ends to take account 

 of the variability of their personal characteristics in talking and listen- 

 ing to the telephone and of the conversational material and conditions, 

 a rating can be placed on the service afforded. By making such obser- 

 vations on connections having different transmission characteristics, 

 relative ratings can be established for these various transmission 

 characteristics. 



It should be recognized, however, that while the rate of repetitions 

 required can be used for relative ratings of the transmission service 

 performance of different circuits, such ratings in themselves do not give 

 a complete picture of the service from the users' standpoint because 

 they do not show directly the amount of effort required. Some idea of 

 the effort exerted can be formed by the observers who are noting the 

 repetitions but this cannot be quantitative. In addition to the repeti- 

 tion rate and effort there is undoubtedly another factor which affects 

 the users' opinion of the service. In conversing over a circuit having a 

 poor transmission performance, annoyance or irritation may be felt by 

 the users because the amount of effort required may be considered by 

 them to be unreasonable. These factors, by their smallness or large- 



