THROWDOWN MACHINE FOR TRAFFIC STUDIES 359 



link frame delays. Taken together, these various delays determine over- 

 all grade of ser\^ce. 



An interesting example of the practical utility of the throwdown 

 machine is furnished by the series of events which lead to the introduc- 

 tion of reversed gate preference in the Xo. 5 crossbar system. The chang- 

 ing quantities of line and register pegs in the gate position provide a 

 graphic visual indication of the dynamic status of the system. After 

 watching the gate for some time in the early overload runs, it was no- 

 ticed that the register marker connectors were relatively less successful 

 in gaining access to markers than the line link frame marker connectors. 

 During all register busy periods, this reduced the call handling capacity 

 of the system since registers were delayed in becoming available to 

 waiting lines. The effect was compounded by wasting marker time in at- 

 tempting to set up dial tone calls when no registers were idle. 



It was felt that a change in gate preference, placing register marker 

 connectors before line link frame marker connectors, would improve this. 

 The new arrangement was tested and confirmed in throwdown run IV 

 and is now a system standard. 



