Friday afternoon at 1 p.m., the iPhone 7 received instructions to isolate itself until Sunday, July 25 at midnight. However, no alert was triggered on the iPhone 6S.
The app works by using bluetooth radio signals from phones, originally designed to connect devices like wireless headphones, to detect when other phones with the app are nearby.
It then anonymously logs phones that are within two meters for about 15 minutes and triggers an alert if the owner of a registered phone records a positive Covid test.
Jon Crowcroft, a professor of computer science at the University of Cambridge who developed the UK’s first digital contract tracing app in 2009 in response to swine flu, said Bluetooth technology was not designed for follow the proximity of people.
He said it was reused for contact tracing to use a number of signals from Bluetooth bounce on nearby phones to “estimate” how close other people are and for how long.
However, while the UK app was very accurate compared to versions in other countries, the signal could be affected by outside factors such as one person having their phone on a table while another had it. had in a bag, which would weaken its ability to detect other devices.