The computer seen in the opening credits is made up from components of an IBM AN/FSQ-7 Combat Direction Central, built in 1954 to protect the US from Soviet bomber attack. It was the largest and heaviest computer system ever built, the full system weighing 6000 tons and taking up an entire floor of a bomb-proof blockhouse. Components of decommissioned systems were sold for scrap and bought by film and television production companies who wanted futuristic looking computers, despite the fact they were built in the 1950s. The components used in this episode were previously used in 'The Time Tunnel (1966)', 'The Towering Inferno (1974)', 'Independence Day (1996)', 'Fail Safe (2000) (TV)' and 'Austin Powers in Goldmember (2002) ' amongst many others.