RELIABILITY OF RADIO TELEPHONE CIRCUITS 



183 



Fig. 1— Idealized illustrations of (a) the day-to-day variation of noise-to-signal 

 ratio and its effect upon lost circuit time, {h) the effect upon lost circuit time of trans- 

 mission improvements and (c) the effect upon lost circuit time of a change in the 

 maximum tolerable noise-to-signal ratio. 



consequently lowered to position A'. Assuming the noise-to-signal 

 requirement B remains the same the lost time is reduced to the interval 

 C. If instead of applying a transmission improvement we increase 

 the tolerable noise-to-signal requirement for a useful circuit or degrade 

 the standard requirement by x db in the case of Fig. 1 (a), the hori- 

 zontal line B is shifted upward x db as shown in Fig. 1 (c) and the lost 

 time corresponds to that for the case of x db transmission improvement 

 in Fig. 1 (b). 



