REMOTE CONTROLLED LINE CONCENTRATOR 



267 



a line or trunk mark alone should not be able to fire a crosspoint diode 

 on a busy line or trunk. 



When the crosspoint operates, a gate which has been inhibiting pulses 

 is forward biased by the —65 volt signal through the crosspoint relay 

 winding. The pulse which initiates the mark operations at the concentra- 

 tor then passes through the gate to return a line busy signal to the central 

 office over this control pairs which is interpreted as a crosspoint closure 

 check signal. 



f. Crosspoint Release Circuit 



The hold magnet of the central office crossbar switch operates, remov- 

 ing the +100- volt operate mark signal after the crosspoint check signal 

 is received. A slow release relay per trunk is operated directly by the 

 hold magnet. When the central office connection in the No. 5 crossbar 

 system releases, the hold magnet is released. As shown in Fig. 14, with the 

 hold magnet released and the slow release relay still operated, a — 130- 

 volt signal is applied in a simplex circuit to the trunk to break down a 

 gas tube provided in the trunk circuit at the concentrator. This tube in 



CONCENTRATOR 



CENTRAL OFFICE 



TO ALL CROSSPOINTS 

 SERVED BY SAME TRUNK 



130V I 



Fig. 14 — Crosspoint release circuit. 



