THROWDOWN MACHINE FOR TRAFFIC STUDIES 



313 



0.6 



O 



>- 



=! 0.4 

 CD 



< 



to 



a 

 0.2 



300 400 



TIME, T, IN SECONDS 



500 



Fig. 7 — Distribution of holding times. 



GENERAL PLAN OF THE MACHINE 



The broad plan of the throwdown involves a division of work be- 

 tween the team of operators and the circuits of the machine. The circuits 

 keep track of system events, resolving complex sequences of actions 

 concurrently taking place. Their chief purpose is to present signals to 

 the four operators so that they mil be able to perform the right actions 

 at the proper time and thus dovetail together the events for a large 

 number of calls in progress. 



The operators keep manual records of the busy-idle states of items 

 which occur in large quantities, such as lines, trunks and links. They also 

 perform the searching operations necessary to locate these items when 

 they are required to be made busy or idle. 



In general the circuits signal the operators to perform actions; the 

 operators in turn signal the circuits that the action is completed or some 

 appropriate alternative taken. The circuits then determine the next action 

 and present corresponding signals to the operators. Thus the circuits 

 largely control the sequencing of events. However, in some cases where 

 the sequencing would require extensive circuitry, the operators assist 

 in determining sequence. For example calls returning to the control 

 circuits after a subscriber completes dialing are interleaved with new 

 calls according to written records maintained by the operators. Releasing 



