This BBC article from 2014 suggests that the call clearing time was reduced to a few seconds by most carriers: https://www.bbc.co.uk/news/technology-26559554 ht

This BBC article from 2014 suggests that the call clearing time was reduced to a few seconds by most carriers: https://www.bbc.co.uk/news/technology-26559554 https://www.bbc.co.uk/news/technology-26559554