Semi-Automatic Ground Environment (SAGE), was a defense network equipped by US military in ‘50s, to track foreign bomber attacks. The project engaged around 800 programmers and several technical employees from America ’s predominant corporations. SAGE was operational by 1963 until 1983, aided by IBM and MIT, the two major contractors who were involved in the project.
Semi-Automatic Ground Environment (SAGE) is considered to be the first giant computer network that provided a real time man-made interface, holding around 55,000 vacuum tubes. They weighed approximately 250 tons and occupied half an acre of floor space. The power consumption by this giant machine was estimated to be 3 MW. SAGE sites were associated to several radar stations, capable of sending data in digital form, prepared from analog inputs. The data is then passed over telephone lines using modems. SAGE computers capture this data to be displayed on cathode ray tubes (CRT) as icons. The SAGE operators were also provisioned to request height data from their CRTs, which were converted to digital forms and transmitted to radar stations, where targets are tracked. Height requests now become available to an operator by moving height cursors, which are centered on the target, and are updated to the source in the same way as it was received. SAGE also enabled operators to choose responses. SAGE comprised of reports to update the system with weapon and aircraft availability. Choosing any of these options would send an order to local controllers through teletypes. The normal interaction between SAGE centers and corresponding intercept aircraft were dispatched through radio equipments. The core component of SAGE system, referred to as “Clyde,” provided data containing intercept of anonymous aircrafts.
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