REMOTE CONTROLLED LINE CONCENTRATOR 



283 



pulses and to permit pulses through amplifier OPA to start the out- 

 pulsing of line selections. These pulses pass to the VGP and VFP leads 

 as long as the VG and VF line selection counters have not reached 

 their first and last stages respectively. The output pulses to the con- 

 centrator are also fed into the drive leads of these counters so that, as 

 the counters in the concentrator are stepped up, the counters in the 

 central office line selection circuit are stepped down. When the first 

 stage of the VF counter goes on, the VF pulses are no longer transmitted 

 until the first stage of the VG counter goes on. This insures that a VF 

 pulse is the last to be transmitted. Also this pulse is not transmitted 

 until the other frame circuits have successfully completed selections of 

 an idle concentrator trunk. Then bi-stable circuit VFLD is energized, 



TO ORIGINATING 



CALL DETECTOR 



I 



VF- 



FROM 

 VG U SCANNER 

 PULSE 

 GENERATOR 



FROM LINE 

 [-SELECTION 

 CIRCUIT 



Fig. 27 — Concentrator control trunk circuit. 



