Wikipedia
Tie line
A tie line, also known as a tie trunk, is a telecommunication circuit between two telephone exchanges or two extensions of a private telephone systems.
Usage examples of "tie line".
Renie found a barge pole and used it to unhook the tie line, then Azador got the engine started and they chugged slowly out onto the dark river.
After pulling the tie line loose, he began wading back, towing the boat quietly behind him.
It felt like C4 had been rigged to that definition, then exploded, and his soul had caught the shrapnel, took the impact as the blast whipped up the tie line.