However "a fast device that measures return latency on the shorted circuit" is presumably very cheap today.
20+ years ago, rewiring buildings for 1000baseT the Cisco switches (3650s maybe? 3750s? I know they had IPv6 multicast acceleration in the switch fabric because that's why we had them) would do this for any circuit on command, OK, 18 metres from here there's a fault, pace, pace, pace, I reckon it'll be up on this cable tray... yup, some fool tried to "repair" a broken Cat5 cable, we'll just rip it out, meanwhile patch to a different circuit.
