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RCC-Remote Call Control also known as third-party call control is provided by CSTA-Computer Supported Telephony Applications. CSTA was developed by the European Computer Manufacturers Association (ECMA) and subsequently was formally standardized by the ITU-T, incorporating the Switch-to-Computer Applications Interface (SCAI). CSTA is an OSI protocol stack that provides an open system interface to a PBX-Private Branch eXchange, ACD-Automatic Call Distributor or CO-Centrex central office switching. CSTA uses, among other technologies, SALT-Speech Application Language Tags specification and its SMEX-Simple Messaging Exchange element, telephony call control capabilities in MSS-Microsoft Speech Server to allow a developer to create sophisticated telephony-based speech applications that can exploit both basic call control services such as ANI-Automatic Number Identification (caller ID) and DNIS-Dialed Number Identification Service (800), using the included basic call controls, or extended call control services, to create custom call controls.