REMOTE CONTROLLED LINE CONCENTRATOR 291 



trunk would be observed without knowledge of the originating line num- 

 ber. For this purpose a regular line observing shoe was connected to 

 one of the ten concentrator trunk switch verticals in the trial equipment 

 and from here connected to the service observing desk in the usual 

 manner. 



The basic service observing requirements in connection with line 

 concentrator operation have not as yet been fully determined. How- 

 ever, it appears at this time that the trunk observing arrangement may 

 be preferable. 



e. Service Denial 



In most systems denial of originating service for non-payment of 

 telephone service charges, for trouble interception and for permanent 

 signals caused by cable failures or prolonged receiver-off-hook conditions 

 may be treated by the plant forces at the line terminals or by blocking 

 the line relay. To avoid concentrator visits and to enable the prompt 

 clearing of trouble conditions which tie up concentrator trunks, a ser- 

 vice denial feature has been included in the design of the central office 

 circuits. 



This feature consists of a patch-panel with special gate cords which 

 respond to particular time slots and inhibit service request signals pro- 

 duced by a concentrator during this period. In this way service requests 

 can be ignored and prevent originating call service on particular lines 

 until a trouble locating or other administrative procedure has been 

 invoked. 



f. Display Circuit 



A special electronic switch was developed for an oscilloscope. This 

 arrangement permited the positioning of line busy and service request 

 pulses in fixed positions representing each of the 60 lines served. Line 

 busy pulses were shown as positive and service request pulses as negative. 

 This plug connected portable aid, see Fig. 32, was useful in tracing calls 

 and identifying lines to which service may be denied, due to the existence 

 of permanent signals. 



Other circuits and features, too detailed to be covered in this paper, 

 have been designed and used in the field trials of remote line concen- 

 trators. Much has been learned from the construction and use of this 

 equipment which will aid in making the production design smaller, 

 lighter, economical, serviceable and reliable. 



Results from the field trials have encouraged the prompt undertaking 



