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Are you asking if the caller will go straight to vm hence feeling "dumped" or will it ring for them like you just missed the call?
 
Apple's very own website explains exactly what it does and how it differs from silence. And if Apple's site isn't sufficient, it's all over Google.

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Are you asking if the caller will go straight to vm hence feeling "dumped" or will it ring for them like you just missed the call?

Ahh this would make more sense. It sends them straight to voicemail to my knowledge.
 
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