Operations Centre (UK RAOC) located at RAF Booker to alert the nation to an imminent air attack. Once an alert was initiated the national and local television and radio networks would break into transmissions and broadcast a warning (the warning message would originate from an emergency studio in BBC Broadcasting House in London). Simultaneously the national air raid siren system would be brought into service. A system, which used the same frequency on normal telephone lines as the peacetime speaking clock, was employed for this whereby a key switch activation alerted 250 national Carrier Control Points or CCPs present in police stations across the country. In turn the CCPs would, via a signal carried along ordinary phone lines, cause 7,000 powered sirens to start up. In rural areas, around 11,000 hand powered sirens would be operated by postmasters, rural police officers, or Royal Observer Corps personnel (even parish priests, publicans, magistrates, subpostmasters or private citizens could be involved in some remote rural areas). Linked into the system were the twenty-five Royal Observer Corps (ROC) group controls, also with direct links to the carrier control points. In the event of subsequent radioactive fallout, local fallout warnings could be generated from the group controls on a very localised basis over the same carrier wave system. The national warning system saw many changes over the years. During the 1960s and 1970s, much of the local authority civil defence planning in the United Kingdom became outdated, although the WB400/WB600 warning system was maintained and kept serviceable along with updating of ROC instrumentation and communications. The system's main problem was that many of the telephone lines it needed had to be manually switched in times of pre-war tension by Post Office telephone engineers. The links were not hardened against the effects of EMP. In the late 1970s and early 1980s heightened fears and tensions led to a resumption of contingency planning and the upgrading of many systems. The outdated WB400/WB600 systems were replaced with brand new WB1400 equipment, communications links were made permanent and hardened against EMP disruption. Sirens The national siren system originating from World War II had a secondary role of "general warning", particularly for imminent flooding. Following the end of the Cold War, a telephone-based system was thought to be more appropriate for national warnings and less expensive to maintain. Additionally the Government retains an ability to break into television and radio