Those settings mostly depend on your mobile carriers and their timers, they need to be fined tuned by testing on your deployment, and depending on the behavior you want.
With those settings, assuming the carrier directs you to some sort of message (not available) or to the carrier's VM, the call to the mobile will be dropped as it was answered in less than 1.5 seconds.
The internal phone, will still ring, those only affect the SNR devices.
This is basically a "shared line"
HTH
java
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