This CoriantTypesYesNo switch (default no) specifies whether an STM-64 (10 Gb/s SDH) client port sends out a specific replacement signal during the client-shutdown holdoff period, intended to prevent downstream equipment from taking its own corrective action while this node is still waiting out the timer. An administrator enables this so far-end or downstream devices see a well-defined signal during the holdoff window instead of either the failing signal or an abrupt gap. For example, enabling holdoff-signal on STM-64 ensures that during the brief window before a client shutdown takes effect, downstream equipment sees a controlled signal rather than reacting unpredictably to a fault still being confirmed.