AUTOMATIC SWITCHING SYSTEM 



403 



single control circuit is provided. The control circuit holding time, in 

 turn, consists of three parts: operate and release times of connector 

 relays, line testing and "marking" times, and the operate time of the 

 switches and junctors. The average liolding time for the control circuit 

 of the switching network for the system described was about 40 milli- 

 seconds. This is considerably shorter than the maximum 50 milliseconds 

 permissible under the heavy traffic conditions of the preceding para- 

 graph. 



SYSTEM OPERATION 



An experimental skeletonized ECASS constructed for laboratory tests 

 is shown in Fig. 11. The equipment is located on these frames from left 

 to right as follows: Frame No. 1, line and originating actuator circuits, 

 switching network and controls; Frame No. 2, trunk, outward actuator 

 and number group circuits; Frame No. 3, originating receiver circuits; 

 Frame No. 4, powder supplies; and Frame No. 5, terminating receiver 

 circuits. 



Without further detailed description of the various component cir- 

 cuits the successful placing of a call through the system may now be 

 traced by reference to the block diagram of Fig. 12. 



Fig. 11 — Skeletonized laboratory model of ECASS. 



