318 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1953 



tions, the gate position being jointly served by the operators stationed at 

 the originating and marker positions. Each operator is given the same 

 name as the position at which she is stationed. 



The general plan of traffic flow is such that all calls are originated or 

 restarted at the originating position. For this reason, the major equip- 

 ment items of this position include: the subscriber line array, which 

 represents by pegs all of the subscriber lines associated with the switch- 

 ing system under throwdown evaluation; the trunks incoming to this 

 system; and certain of the system components associated with incoming 

 calls. The call slips, sorted in sequence as to originating times, are stored 

 at the originating position for use in originating calls. 



Means are provided for presetting the times at which the next origi- 

 nated or restarted calls will enter the throwdown machine. When actual 

 time coincides with a time thus preset, the system stops and signals the 

 originating operator to serve the waiting item. The originating position 

 does not provide for actually entering an item into the machine, but 

 indicates the time of entry, stops the machine, and supplies the items 

 to be entered. For example, the operator, when signalled to originate a 

 dial tone call in accordance with information furnished on the call slip, 

 selects, from the line array, a peg representing the subscriber line, asso- 

 ciates it with the call slip, and passes the two items to the gate for entry. 



Since the means for determining the busy or idle condition of a sub- 

 scriber line are provided by the presence or absence of that line's peg 

 in the array, the originating position also enters into the operation on 

 incoming and intraoffice calls. 



The gate position, which simulates the marker connectors of the No. 

 5 crossbar system, serves as the entry point for all calls. The originating 

 operator inserts call slips and pegs into the gate position from one side to 

 start the call. The marker operator removes them at the other side for 

 processing in the marker position. Relay circuits associated with the 

 gate position control the flow of traffic through the gate in accordance 

 with actual No. 5 crossbar operation. 



The marker position provides means for associating the call slips 

 with the individual simulated markers of the switching system. Since 

 these markers control processing of the calls, the principle records of 

 the calls' progress are obtainable through this association. The records 

 are kept as time entries on the call slip and marked adjacent to action 

 lamps determining these entries. 



At the top of each marker unit in the marker position are cords which 

 provide access to the switching system components under control of 

 the marker. These components are line link frames, number groups, 

 sender subgroups, and marker connectors. As the call progresses, the 



