From Cisco Unified CM Administration > System > Service Parameter Configuration
Wait Time Before Forwarding Unanswered Calls (if specified)
Found in section “Clusterwide Parameters (Feature – Forward)“
Parameter title Forward No Answer Timer
Default Value is 12 seconds, approximately 4 seconds ring cycle.
WARNING: This Call Forward No Answer (CFNA) feature is a Global parameter, changing the value will affect all phones in the network.
Redirect Unanswered Calls to Next Target
Found in section “Clusterwide Parameters (Feature – Redirection [3xx])”
Parameter Title “Redirection Ring No Answer Reversion Timer“
Default Value is 24 seconds, maximum 180 seconds.