Asterisk (telephone system)

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Asterisk

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Basic data

developer Mark Spencer
Publishing year 1999
Current  version 17.6.0 (Standard)
Jul 16, 2020

16.12.0 ( LTS )
16. Jul. 2020

13.35.0 ( LTS )
Jul 16, 2020

operating system Unix derivatives
programming language C.
category IP telephony
License GNU GPL
German speaking No
www.asterisk.org

Asterisk is free software for computers of all types that offers the functionality of a telephone system . It supports IP telephony (VoIP) with different network protocols and can by hardware with connections such as POTS (analog phone line), ISDN - Basic Rate Interface (BRI) or - Primary Rate Interface (PRI, E1 or T1 ) are connected.

Mark Spencer originally developed Asterisk at Digium. In the meantime, other developers have joined the Asterisk community and so many extensions and applications also come from other developers. The name comes from the name for the star symbol .

Asterisk is made available under a dual license - the GNU General Public License (GPL) as a free software license and a proprietary license that allows licensees to deliver proprietary, non-public components.

Functions

Asterisk supports

hardware

Asterisk works on a number of different computer systems . In addition to personal computers with x86 processors , Asterisk also runs on devices such as the Raspberry Pi and routers that support OpenWrt .

An Asterisk system can only be connected and operated without special hardware via a network with (internally) VoIP terminals and (externally) VoIP telephone providers.

For the connection (externally) on traditional phone networks or (after internal) of normal terminal devices such as telephones, fax machines etc. one additional required plug-in cards or external analog adapter for analog POTS and digital ISDN - trunks (externally) or extensions (to internal ).

Internal ISDN extensions can only be implemented using interfaces that support NT mode (ISDN cards with HFC chips or VoIP adapter / router with internal ISDN connection).

Configuration and programming

The central control element of Asterisk is the call number or better dialing plan (English dial plan ). Here is decided:

  • where a caller is forwarded (to which terminal)
  • what happens if no one answers there or it is occupied
  • which answering machine / mailbox should be informed
  • which entries (digits, language) are accepted
  • which action is triggered by an input

This plan is divided into several sections (English sections ), whose names are passed in square brackets. A section is valid until the next opening bracket or the end of the file. Within the sections, a specific group of extensions and the related sequences, actions and behavior are dealt with. The sections "[general]" and "[globals]" are predefined sections. All other sections are also referred to as contexts. Contexts determine a closed area and thus a defined security area. A context can acquire the security area of ​​another context by including it in this context using the include statement. If no context is defined for an extension, it is handled via the standard context "[default]".

Interfaces

Operating systems

Asterisk can run under the following operating systems :

VoIP protocols

ISDN / PRI protocols

Local interfaces

In addition to the aforementioned protocols, Asterisk also offers the use of local interfaces with the modules chan_alsa and chan_mobile. This makes it possible to use an existing sound card as a microphone unit. A Bluetooth headset can also be registered directly as an extension. A cell phone / smartphone becomes a cellular gateway via Bluetooth.

These possibilities are mainly used in the private environment, since they can naturally only be used in the immediate vicinity of the Asteriskserver.

Audio codecs

The following audio codecs, among others, are supported:

Programming interfaces

The AGI Asterisk Gateway Interface offers, among other things, a programming interface to:

GUIs and distributions

Graphic user interfaces enable the Asterisk configuration to be edited via the web interface. The following Asterisk server distributions contain Linux or BSD and are now mostly commercial products, which, however, have their roots in free projects and are free of charge in the basic versions or for private users.

  • Asterisk4UCS is an infrastructure management solution for Asterisk-based telephone systems, based on the Linux distribution Univention Corporate Server (UCS). It enables the telephone infrastructure to be managed with a graphical web GUI and linked to LDAP. Central Asterisk telephone functions are also offered. The solution is based on the open source license GNU GPLv3 and can be used free of charge. Support and maintenance, however, is chargeable.
  • Ansitel webinterface 3.0 is a completely German / English language web interface for Asterisk-based telephone systems, which implements a simple and fast setup. A limited live CD is available for download as a quick start.
  • AsteriskNOW is a distribution including Asterisk control created by Digium. The Asterisk Business Edition from Digium includes an optional distribution.
  • AskoziaPBX is an easy-to-configure commercial live Asterisk system, based on Linux , with a WebGUI, which is aimed at both professional users and beginners. A trial version for up to 2 simultaneous connections is available. (The AskoziaPBX was discontinued when it was taken over by 3CX in August 2017. Support will end at the end of 2017.)
  • AstLinux is a resource-saving version with additional router and VPN functionality that runs from a flash memory . The current version is 1.3.5.2 (as of February 2019).
  • Astimax is a commercial professional VoIP appliance based on Asterisk with a graphical administration tool .
  • FreePBX , a web-based open source GUI under GPL.
  • Community is the name of an open source telephone system that is based on Asterisk up to version 3. From version 4, FreeSWITCH forms the basis.
  • KITOMA is a scalable and easily integrated VoIP all-in- one solution based on Asterisk. A web-based user interface is made available which can be operated intuitively and offers an open REST interface for flexible connection of applications. The current Asterisk version can always be used! The number of manageable Asterisk servers is arbitrary.
  • pascom is an Asterisk-based Unified Communications solution. A free tariff package limited to 2 simultaneous ( concurrent ) users is also available.
  • STARFACE Based on the Asterisk Business Edition with a graphical interface for easy operation. Available as a software solution, VoIP appliance and as a cloud service. Free version available for up to 3 users.
  • Thirdlane PBX and Thirdlane Multi Tenant PBX are Asterisk-based PBX software solutions. They are aimed at businesses and internet telephony service providers.
  • Trixbox emerged in May 2006 from the Asterisk @ Home project .
  • VoIPonCD is a freely available VoIP telephone system.

Speech modules (voice prompts)

Language modules are required to use the Asterisk voicemail system with local language. These are collections of required letters, numbers and words for a speaker and not text-to-speech or speech synthesis modules.

  • Digium does not offer any German language modules.
  • voip-info.org (English) offers many different languages, from Chinese to Turkish.

Web links

Individual evidence

  1. ↑ wiki.asterisk.org . (accessed on January 21, 2018).
  2. ↑ github.com . (accessed on January 21, 2018).
  3. ↑ Changelog 17.x. In: asterisk.org. Retrieved July 11, 2020 .
  4. ↑ Changelog 16.x. In: asterisk.org. Retrieved July 11, 2020 .
  5. ↑ Changelog 13.x. In: asterisk.org. Retrieved July 11, 2020 .
  6. ↑ Stephen P. Olejniczak, Brady Kirby, "Asterisk For Dummies"
  7. ↑ Jim Van Meggelen, Jared Smith, Leif Madsen, "Asterisk: The Future of Telephony"
  8. ↑ a b asterisk.org Retrieved August 30, 2012.
  9. ↑ asteriskwin32.com. Retrieved August 30, 2012.
  10. ↑ Voip-Info.org: Asterisk codecs , accessed on August 30, 2012.
  11. ↑ a b Asterisk telephone system in version 10, C't issue 25, November 21, 2011, p. 36.
  12. ↑ Das-Asterisk-Buch.de: Chapter 20. Asterisk Gateway Interface (AGI) , accessed on August 30, 2012.
  13. ^ AGI Libraries and Frameworks. August 5, 2016, accessed August 5, 2016 .
  14. ↑ voip-asterisk.info: Asterisk4UCS . Retrieved February 20, 2013.
  15. ↑ Ansit-com.de: Ansitel web interface . Retrieved March 26, 2013.
  16. ↑ Asterisk-berlin.de: Ansitel Webinterface 3.0 - limited Live CD as download . Accessed on March 26, 2013.
  17. ^ Asterisk.org Retrieved August 29, 2012.
  18. ↑ Askozia.com: Askozia - Intuitive telephony Accessed on August 29, 2012th
  19. ↑ 3CX press release of August 3, 2017: "3CX continues to expand after the takeover of Askozia" .
  20. ↑ astlinux-project.org Retrieved August 29, 2012.
  21. ↑ Astimax.de: Astimax VoIP systems
  22. ↑ freepbx.org Retrieved August 29, 2012.
  23. ↑ Golem.de: Community 4.0 - Free and secure telephone system for the BSI. Retrieved on August 29, 2012.
  24. ↑ voip-asterisk.info: KITOMA Retrieved on March 7, 2016.
  25. ↑ pascom.net: Voice over ip telephony at its best | pascom.net Retrieved September 20, 2018.
  26. ↑ Starface.de: The STARFACE product family.Retrieved on August 29, 2012.
  27. ↑ Thirdlane.com Third Lane IP PBX Products
  28. ↑ Fonality.com trixbox Line of Asterisk based IP PBX Products Accessed on August 29, 2012th
  29. ↑ VoIPonCD by rowi.net Retrieved on August 29, 2012.
  30. ↑ voip-info.org: Asterisk sound files internationally Accessed on August 29, 2012th