Vivotek NR9682-v2 64-Channel NVR (No HDD) - Manual (Page 149)

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User's Manual - 149
The Sound the alarm action provides 5 alarm sounds that will be sounded on the VAST client or server.
Your VAST client or server should have speakers for playing the audible alarm.
A reacheable Mail server and Email accounts must be provided before you can apply the settings.