One final 'phone story I was told . A Scampton Vulcan crew visited the war room in Cheyenne Mountain in the 60's and were shown the American system where the duty officer could be phoned on any Nuclear base and had to reply within three rings. They were invited to select a base in the USA and this was duly demonstrated. They were assured that this system also extended to appropriate RAF Bases.
At their request this was duly initiated as a demonstration for their home station.
After a couple of rings a female voice announced:
" All lines to Lincoln are currently engaged . Please call later "