The Play Prompt block, if selected as Resource, is an static audio file you select in the block properties.
You can use dynamic paths too, it is like a common HTML/Javascript routines to load an image in a web site for example.
As for the Busy/Silence, those names are determined at SIP Server options.
The VOX and WAV extensions are actually defined at your language js file (Resources folder/Lang pack)
/**
* Default audio file extension
*/
var audioFileExtension = ".wav";
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Jorge Cornejo
VS Telecom LTDA.
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