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Asterisk is a software implementation of a telephone private branch exchange (PBX); it allows attached telephones to make calls to one another, and to connect to other telephone services, such as the public switched telephone network (PSTN) and Voice over Internet Protocol (VoIP) services. Its name comes from the asterisk symbol, *. Asterisk is released with a dual license model, using the GNU General Public License (GPL) as a free software license and a proprietary software license to permit licensees to distribute proprietary, unpublished system components. Asterisk was created in 1999 by Mark Spencer of Digium. Originally designed for Linux, Asterisk runs on a variety of operating systems, including NetBSD, OpenBSD, FreeBSD, Mac OS X, and Solaris. Asterisk is small enough to run in an embedded environment such as Customer-premises equipment-hardware running OpenWrt.〔(【引用サイトリンク】title=Asterisk on OpenWrt )〕 There are complete self-contained versions that can boot from a storage device such as a flash drive or external disk drive (preferably IDE/PATA, SATA or mSATA; a USB-connected device can be used, but is often not recommended).〔(AstLinux: Boot via USB Flash Storage ). "For production AstLinux installations, it is recommended to use flash storage connected off IDE, SATA or mSATA controllers ... it takes longer for USB storage devices to be recognized ... AstLinux may fail ... followed by the USB drive mounting a few seconds later."〕 A live CD or virtual machine can also be used.〔(【引用サイトリンク】title=AstLinux Users Guide Chapter 1 )〕 ==Features== The Asterisk software includes many features available in proprietary PBX systems: voice mail, conference calling, interactive voice response (phone menus), and automatic call distribution. Users can create new functionality by writing dial plan scripts in several of Asterisk's own ''extensions'' languages, by adding custom loadable modules written in C, or by implementing ''Asterisk Gateway Interface'' (AGI) programs using any programming language capable of communicating via the standard streams system (stdin and stdout) or by network TCP sockets. Asterisk supports several standard voice over IP protocols, including the Session Initiation Protocol (SIP), the Media Gateway Control Protocol (MGCP), and H.323. Asterisk supports most SIP telephones, acting both as registrar and back-to-back user agent, and can serve as a gateway between IP phones and the public switched telephone network (PSTN) via T- or E-carrier interfaces or analog FXO cards. The Inter-Asterisk eXchange By supporting a variety of traditional and VoIP telephony services, Asterisk allows deployers to build telephone systems, or migrate existing systems to new technologies. Some sites are using Asterisk to replace proprietary PBXes, others provide additional features, such as voice mail or voice response menus, or virtual call shops, or to reduce cost by carrying long-distance calls over the Internet (toll bypass). Asterisk was one of the first open source PBX software packages. In addition to VoIP protocols, Asterisk supports traditional circuit-switching protocols such as ISDN and SS7. This requires appropriate hardware interface cards, marketed by third-party vendors. Each protocol requires the installation of software modules. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Asterisk (PBX)」の詳細全文を読む スポンサード リンク
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