A transmission line connecting parts of a system, especially a telephone line connecting two private branch exchanges.
 Example sentencesExamples
-  Queuing for callers on hold is performed at the edge of the network, helping reduce the need for overflow ports and expensive tie lines between multisite contact centers.
 -  We utilized radio tie lines.
 -  The access points are interlinked with additional infrastructure including switches and tie lines.
 -  They connect only through tie lines where power must be converted from alternating current to direct current and back again.