The name of a bunch of linked geographically distributed telex machines. Like a phone network but for text? Uh, actually, I guess what they built it something l

The name of a bunch of linked geographically distributed telex machines. Like a phone network but for text? Uh, actually, I guess what they built it something like email? And the central hub had a simulator that could help with taking decisions based on the input from that data? They als had a very swell control room.