388 BELL SYSTEM TECHNICAL JOURNAL 



system "A" boards in multi-operating center cities,' to permit the 

 "A" board handling of station-to-station toll calls over such circuits. 



Except that they are arranged for establishing connections to ring- 

 down toll lines only and have certain additional features required 

 thereby, the operating and service features of these toll office tandems 

 are similar to those of the manual straightforward tandem previously 

 described. The trunks from the toll board to the tandem positions 

 are usually of the idle-position indicating, idle-trunk indicating, type. 

 Trunks from "A" boards have the idle-trunk indicating feature only. 



The ringdown toll lines are multipled in the tandem positions and 

 are equipped with idle-indicating lamps. When a tandem trunk is con- 

 nected to a toll line, a ring of two seconds' duration is sent auto- 

 matically, but a ring-release key is provided on each tandem position 

 to permit connection to be made to a toll line without ringing, as is 

 necessary under certain operating conditions. Subsequent rings on 

 the toll line may be made by the originating operator. 



When ringdown toll lines appear directly in the multiple before the 

 originating operator and she finds all of the circuits in a particular group 

 momentarily busy, she ascertains when a circuit in the group becomes 

 idle by observing the busy signals associated with the toll line jacks. 

 When connections to the circuits are obtained through toll office tan- 

 dem equipment, the equivalent of this arrangement for ascertaining 

 when a circuit becomes available may be obtained by providing over- 

 flow circuits connected to jacks associated with the different circuit 

 groups in the toll line multiple at the tandem positions. The tandem 

 operator connects the incoming tandem trunk to the overflow circuit 

 and the first toll line in the group to become idle causes a signal indi- 

 cating this to be given over the trunk to the originating operator. 

 Should the overflow circuit also be busy, the tandem operator connects 

 the incoming trunk to one of a common group of circuits arranged to 

 transmit a signal indicating this condition. 



Figure 5 is a photograph of one of the two toll office tandem switch- 

 boards in the Long Lines Office in New York City. 



In cities not requiring the use of tandem equipment in order to give 

 toll board operators access to the toll lines, a somewhat different toll 

 tandem arrangement is provided for giving " A " operators access to the 

 toll board circuits. Under these conditions the tandem operators' 

 positions are located in line with the toll positions, and the incoming 

 trunks may or may not have the automatic listening feature described 

 in connection with manual straightforward tandems. If not, the 



^ A multi-operating center city is one sufficiently large to require the local operat- 

 ing to be distributed between two or more buildings. 



