The building that housed the SAGE computers was call a direction center. The computer gathered information from RADAR sites all around the area that was being monitoured, in my case the N.W. corner of the country and lower portion of Canada. There was a room that had situation displays where operators would watch a section of air space. If they got a trace they would use a light gun to highlight the track and the computer would the attempt to identify it by means of a transponder. If there was no answer back from the air craft the track was then handed over to the seinor director who would then try to identify the track and if he couldn’t he would make the call to scramble fighter planes to greet the offender. To my knowledge no planes were ever shot down. In a nut shell thats how the system worked. Hope this answers some of your questions.
my dads time was early 60’s