asterisk PBX sound files - en-us/gsm

 Asterisk is an Open Source PBX and telephony toolkit. It is, in a
 sense, middleware between Internet and telephony channels on the
 bottom, and Internet and telephony applications at the top.
 .
 Asterisk includes a set of standard sound files in various formats.
 This package contains the core part of that collection in English (US,
 by Allison Smith) in raw gsm-fr format (Compressed. Takes relatively
 little space. playable with sox).