1120 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1952 



As improvements in the art are made they can more readily be in- 

 corporated in common control systems than in step-by-step systems. 

 For example, new subsets which may employ keys or other sending 

 devices different from the dial can be accommodated by provision of 

 proper facilities in senders and registers. Also, improved high speed 

 pulsing arrangements can be easily incorporated in systems which do 

 not require the switches themselves to be directly driven by pulses from 

 the calling device. 



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