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CSTA = Computer Supported Telecommunications Applications


CSTA is a ECMA, ETSI and ISO/IEC Standard with an exhaustive feature set and a comprehensive call model.

CSTA supports, with the same call model, Voice and Non-Voice interactions (Email, Chat, IM and many more) and complements SIP protocol, enabling application developers to provide advanced features.


On 2004 the ECMA international organization has approved the ECMA-269 (6th Edition), best also known as Services and Events Reports for CSTA, as an official standard, together with a series of related publications.


This suite is a complete toolbox for developing a wide range of enterprise grade CSTA applications taking advantage of Internet technologies such as XML, SIP and Speech Recognition and Processing.

CSTA supports a wide range of application scenarios, from basic 1st Party Call Control to advanced 3rd Party Call Control with the same standardised model. CSTA lets application developers to create advanced communication platform features without burdening them with underlying protocol specifications.

Abstraction level

CSTA is an abstraction layer for telecommunication applications:

  • Independent of underlying signaling protocols:
  • Independent of devices:
    • Intelligent endpoints (like SIP workpoints)
    • Low-function / Stimulus devices
    • SIP Signaling models
    • 3rd Party Call Control (3PTY versus P2P)
  • Operates equally well in different environments:


Its basic call model was standardized in 1992 and then continually refined and enhanced based upon significant industry implementation experiences, new protocols and requirements.

Design goals followed to enhance application portability across CSTA implementations:

  • Specifies normalized call model and behavior
  • Complete functional definition of each service
  • Specific conformance criteria


  • CSTA Phase I
    • Published 06/1992
    • 40 Features
    • Focused on Call Control
  • CSTA Phase II
    • Published 12/1994
    • 77 Features
    • Focused:
      • I/O Services
      • Voice Unit services
      • Call Control services
  • CSTA Phase III (CSTA Phase II Features and VERSIT consortium CTI Technology)
    • Published 12/1998
      • 136 Features
      • Published as ISO Standard 07/2000
    • Published CSTA XML (ECMA-323) 06/2004
    • Published "Using CSTA with Voice Browsers" (TR/85) 12/2002
    • Published CSTA WSDL (ECMA-348) 06/2004
    • Published Object Model (TR/88) 06/2004
    • Published "Using CSTA for SIP Phone User Agents CSTA (uaCSTA)" (TR/87) 06/2004

See also / Siehe auch