This Integer32 (250..65535), in milliseconds, defines the hangover time for Voice Activity Detection, i.e. how long the gateway waits after detecting voice inactivity before activating silence suppression. This delay prevents VAD from clipping the tail end of speech by waiting a bit after apparent silence begins before actually suppressing transmission, which an admin tunes to balance bandwidth savings against speech clipping risk. For example, if users report that the ends of their sentences are getting clipped on VoIP calls, an admin might increase vismVoIpVADTimer to give more hangover time before silence suppression kicks in.