272 



BELL SYSTEM TECHNICAL JOURNAL 



elusion is confirmed by the tests made with no delay between the sup- 

 pressors, in which lockout is obviously impossible with synchronous 

 action, but in which lockouts were actually obtained in amount con- 

 sistent with the rest of the data. 



Figures 5 and 6 show that the number of lasting and releasing lock- 

 outs can be calculated from the circuit constants and the distributions 

 of response and resumption times. Approximations which are suffi- 



§ 0.7 



o 

 u 



UJ 



'^ 0.6 



S 0.5 



0.2 



0.1 



0.1 0.2 0.3^ 0.4 0.5 0.6 0.7 



he + hw IN SECONDS 



Fig. 7 — Observed length of lockout as a function of relay hangovers. 



cient for practical purposes for calculating the number of lasting and 

 releasing lockouts are respectively 



Li = 0.9 + 11.0 /J, 

 Lr = 0.9 + 17.7 p. 



(3) 

 (4) 



The duration of a lockout is obviously dependent upon the way in 

 which the subscribers talk and upon the hangovers of relays hw and h/. 

 Lockouts of several seconds duration have frequently been observed but 

 most frequently the duration of lockouts appears to be short and de- 

 termined primarily by the relay hangovers. Figure 7 shows the mean 

 duration of lasting lockouts plotted as a function of the sum of the relay 

 hangovers, he + hw' ■ The straight line is the least square representa- 

 tion of the data, which is 



Di = 0.002 + 1.16 (//. + /;,/). 



(5) 



The constant term in this equation can be neglected for approximate 

 calculations. 



