Atomic Bomb Alarm: Early Days of Early Warning In the 1960s, The U.S. Air Force needed a sure way to know quickly whether Soviet bombers or missiles had struck American cities and bases with nuclear weapons. This small device, part of a nationwide "Bomb Alarm Display System," was designed to send warning signals to military command centers to confirm that an attack had occurred. The Bomb Alarm Display System, operational from 1961-1967, was intended to confirm whether nuclear weapons had detonated in the mainland U.S. or at missile early-warning radar sites in Alaska, Greenland and the United Kingdom. Knowing whether a nuclear attack had actually happened would help leaders decide how to respond, and would help avoid launching missiles by mistake. The bomb alarm network, made by the Western Union Telegraph Co., monitored about 100 military sites and U.S. population centers using sensors like the one on display. At Strategic Air Command, the North American Air Defense Command, the Pentagon and other military headquarters, large electronic maps displayed the whole network. Sensors were mounted on buildings or telephone poles and placed several miles apart around cities and bases. If a nuclear blast occurred, the unit would send a warning signal to a control center before the sensor was destroyed. The bomb alarm was not sensitive to lightning, sunlight, or electrical surges. Photocells inside the glass lens reacted only to the flash of a nuclear explosion. Western Union designed the Bomb Alarm Display System beginning in 1959, and in 1962 the network was complete. One drawback was that it responded only after an attack -- it did not give advance warning. Another drawback was that it relied on commercial telephone or telegraph lines, which could be damaged. Though the bomb alarms made military decision-making more reliable, better communication systems and satellites made the network unnecessary by the late 1960s. Click here to return to the Cold War Gallery.