REMOTE CONTROLLED LINE CONCENTRATOR 



271 



to the gate of the passive line circuit, Fig. 3(b). If the line is idle the 

 pulses are inhibited. If the receiver is off-hook requesting service (no 

 (•rosspoint closed) then the gate is enabled, the pulse passes to the service 

 request amplifier and back to the central office in the same time slot 

 as the pulse which stepped the VF counter. If the line has a receiver 

 off-hook and is connected to a trunk the pulse passes through a contact 

 of the crosspoint relay to the line busy amplifier and then to the central 

 office in the same time slot. 



At the end of each complete cycle a reset pulse is sent from the central 

 office. This pulse instead of the VG pulse places the 12-stage counter in 

 its first position. It also repulses the 5 stage VF counter to its fifth stage 

 so that the next VF pulse will turn on its first stage to start the next 



j cycle. The reset pulse insures that, in event of a lost pulse or defect in 

 a counter stage, the concentrator will attempt to give continuous ser- 

 \'ice without dependence on maintaining synchronism with the central 



I office scanner pulse generator. Fig. 18(a) shows the normal sequence of 



I line scanning pulses. 



, When a service request pulse is generated, the central office circuits 



t] 



04 



r 



VF 5- STAGE 

 COUNTER 



03 



TO 10 



INTERMEDIATE 



GATES EACH 



V 



02 



I 



01 



00 



TO 5 GATES EACH 

 I 



1 23456 789 10 

 I I I I I I I I I I 



I I I I I I I I I I 



VG 12-STAGE COUNTER 



59\ 



58 



57 



56 



55 



GATE PER LINE 



■ FEEDS PASSIVE 



LINE CIRCUITS 



/ 



VG 



RES ET 

 VF 



FROM 



CENTRAL 



OFFICE 



Fig. 17 — Diode matrix for scanning lines. 



