THROAVDOWN MACHINE FOR TRAFFIC STUDIES 343 



As discussed previously, certain marker functions are located at the 

 assignment, originating and match positions. The choice of trunk link 

 frames and trunks, for example, is made at the assignment position. 

 Therefore certain lamps at the marker position light only to signal the 

 writing doAvn of a time. This is true of the second lamp from top left 

 which indicates register seizure. The lamps in the right-hand row are 

 also used in conjunction with actions at other positions. They Hght only 

 to indicate that a delay should be checked in the corresponding box. 



At the time of marker release, both left and right lamps Hght opposite 

 one of the release categories. The specific type of release determines 

 partially the further disposition of the call. 



The START key at the bottom of each marker unit is pressed after 

 completing each action called for by the sequence lamps. Operation of 

 this key puts out the lamp and permits the circuit to advance. 



ASSIGNMENT POSITION 



The assignment position, shown on Fig. 21, includes the trunk array, 

 the register false start holding array, the traffic assignment equipment, 

 the holding time book and counters, and indi\dduals units representing 

 extensions of the markers. The chief function of the assignment operator 

 is to test and choose trunks on each call, to determine the disposition 

 of certain calls which encounter excessive dial tone or busy conditions, 

 and to 'ascertain holding times of originating registers and trunks. 



The trunk array consists of jacks (holes) representing all the trunks, 

 and jacks and pegs representing the registers. Line pegs are held in the 

 jacks during conversation time to mark the trunks busy. The array is 

 divided into vertical sections representing trunk link frames. The trunk 

 groups are disposed in horizontal row^s so that trunk jacks of each group 

 or route occupy the same relative position in each frame section. Thus 

 a trunk-hunting action consists of picking a horizontal level in the array 

 and searching along the level to the first idle trunk as indicated by an 

 empty jack. The array provides more jacks than the total number of 

 trunks so that most small trunk groups can be set up on individual 

 horizontal levels. 



The trunk identification is a three or four digit number composed as 

 follows : 



R— TLF— SW 



where R is route number 0-99 

 TLF is trunk link frame 0-9 

 SW is switch nimiber 0-9 



