London

“You will be glad to hear that I have just received a coded radio signal sent from your father’s expedition shortly before he flew out of range,” he said. “All is well aboard the 13th Floor Elevator.”

“Good!” said Katherine, knowing that it would be the last she would hear of Father until he was on his way home; even the Engineers had never been able to send radio signals more than a few hundred miles

Mortal Engines page 56/152, Chapter 14: The Guildhall

“A single airship, Lord Mayor.” It is a nervous-looking Engineer, a shell-like radio clipped to his ear. “It has pulled clear, but we believe it may have landed a boarding party.”

“Anti-Tractionists on Top Tier?” The Lord Mayor nods, as if this is the sort of little problem that crops up every day. “Well, well. Dr Twix, I think this might be a good opportunity to test your new models.”

Mortal Engines, 138/152, Chapter 33: Wine and Nibbles and the dawn of a new era