It's mind boggling. We've come such a long way as I sit here typing into a computer that's far more powerful than the multi-million dollar computers used in the SAGE air defense system of the '60s. I spent over a third of my career at AT&T working on SAGE and I love to talk about it. You may have worked on it too. It was enormous. Google "sage system."

In the early '50s, at the height of the cold war with Russia, when people were building bomb shelters, it became apparent that America's air defense was woefully inadequate to cope with the "threat." I recall secret documents passing my desk from "think tanks" like RAND that described threats of hundreds of Russian Bison bombers attacking the United States and the paths they might take and damage inflicted. The U.S. definitely had to stop processing air-defense radar data manually as done in WWII and feed it into computers where decisions could be centralized on how to meet a massive attack. Computers were in their infancy then.

It was decided to divide the nation into 23 geographical sectors with each sector having a computer that could accept data from several radar sites each connected by two 1300 bits-per-second private lines. In the reverse direction, data was sent to radio sites co-located with radar that retransmitted it over UHF radio to control interceptor aircraft and missiles using time-division. It was the first real-time computer system ever invented and it was amazing that it worked considering how slow it was. The Direction Center computer used almost 60,000 vacuum tubes, took about 1/2 acre of floor space, weighed 275 tons and required 3 megawatts of power and yet had nowhere near the power of the PC on your desk. A couple hundred people worked in the bomb-proof DC at display consoles handling information from all sorts of agencies such as the FAA and other military units and directing intercept aircraft and missiles. The Boston sector was typical; its DC was located at Stewart AFB in New York and its area of responsibility extended from Maine to Connecticut and from New York to hundreds of miles at sea to radar on Texas Towers, picket ships and seaward-extension aircraft. I remember proposing a radar/radio site on top of Mt. Katahdin that would blanket all of Maine, until we discovered it was snow-bound in the winter and inaccessible.

It wasn't until the mid-60s that SAGE data circuits improved from 1300 bps to 2400 bps using a new technology called "four phase" modulation, about which I wrote an article for an Air Force magazine. It was at this time that SAGE was moved off private lines to a dial-up network called AUTOVON (automatic voice network) designed for nuclear survivability by the Bell System. It was also when Paul Baran of RAND proposed an alternative survivable packet network that ended up as Internet.

Whatever happened to SAGE that took billions of dollars and years to build? It was operational from '62 until '83 when it was replaced by newer systems and airborne control. By the time it was completed ICBM missiles had become the new threat making SAGE useless. But a lot of new technology came from Sage and in peacetime it became more of an air traffic system that influenced the automation of FAA's air traffic control. Those were 12 fun years for me as an engineer. It's hard to believe how technology has changed in computer communications.