THROWDOWN MACHINE FOR TRAFFIC STUDIES 319 



marker operator will connect and disconnect the marker with these 

 components as directed by the action lamps pro\ided. 



The principle purpose of the assignment position is to provide equip- 

 ment for test and choice of a trunk on each call. A trunk jack array which 

 includes all trunks and registers of the s^\'itching system therefore ap- 

 pears on the face of this position. Since, in the actual Xo. 5 crossbar 

 system, testing and choosing of trunks are performed by the markers, 

 an extension of each marker also appears in the assignment position. 

 The assignment operator, when required, makes a visual test for idle 

 trunks to the proper destination. She then chooses and associates one 

 of these idle trunks with the active marker by means of a marker cord 

 which is plugged into the trunk jack. 



In addition to this principal function of trunk choice, the assignment 

 position is equipped to determine the disposition of calls when the marker 

 has finished setting them up. Means for ascertaining conversation time, 

 dialing time and other types of holding times is provided. 



The positions so far described have simulated only the two ends of a 

 connection, the subscriber line and the trunk or register. To complete 

 the connection a channel must be set up between these ends. In the 

 actual switching system the marker matches a line link, a junctor, and a 

 trunk link to form the channel. The match position is provided to 

 simulate this action. The match operator, through visual inspection 

 of a set of channel cards, tests and makes busy the channels for each 

 connection. Information as to the originating subscriber line reaches 

 her through the pass box in the form of the upper portion of the call 

 slip. Fig. 9. Information as to the trunk or register choice is passed ver- 

 bally by the assignment operator. Since this operation is a function of 

 the marker, marker extensions appear at the match position. These 

 extensions are pro\'ided Avith action lamps to guide the match operator 

 and with, keys to inform the simulated marker circuits of the results of 

 the match. 



A pass ^\dndow is cut between the marker position and the assign- 

 ment position for passage of the call slip and originating peg at the time 

 of marker release. Similarly, a pass box is provided for passing the 

 upper portion of the call slip (match ticket) from the match operator to 

 the assignment operator. The assignment operator is charged ^\ith the 

 disposition of these items. 



THE TIME SYSTEM 



The timing system of the throwdo^\'n machine is based on a start- 

 stop system of time pulses. Pulses generated by the clock. Fig. 11, drive 

 indicators wluch display time and also drive circuit elements which 



