Help regarding simultaneous calls

I am using Manager API’s in my application to interact with asterisk. When i am uing originate command to make a call it is successful. When i am trying to execute two originate commands by sending it simultaneoulsy to asterisk only when the first call is answered or ignored the second call rings. Does anybody know the reason for this? Is there any means to execute many originate commands simultaneoulsy? Kindly give a solution for this.