“E very time there is a power failure I lose all means of communication with the outside world,” says Robert Dewar of life in a remote village in the Scottish Highlands since the landlines were transferred from the old copper cable network to broadband connections. Blackouts also knock out the village’s mobile phone signal. “Our most recent power cut lasted for 42 hours,” Dewar says. The interruption outlasted his five-hour emergency backup battery. “If I had had a heart attack there is damn all I could have done about it, except compose myself, say my prayers, and await the outcome.” Dewar was among the more than 100 readers who contacted us with their experiences as the old infrastructure – the public switched telephone network (PSTN) – used to make calls is replaced with digital lines. It is one of the biggest tech upgrades since the analogue television signal was switched off more than a decade ago, a change that forced Britons to convert their TVs or buy a new digital set.…