Phone Technologies

Phone and mobile technologies are my passion. Here are some of the major standards for phone based technologies that I have worked with in the past.


VoiceXML is a Web-based markup language for representing human-computer dialogs, just like HTML. But while HTML presumes a graphical user interface to access information, VoiceXML presumes an audio interface where speech and DTMF tones take the place of the screen, keyboard, and mouse.


CCXML was designed to provide telephony control for VoiceXML (and other dialog languages). Application developers can use CCXML to perform call screening, whisper call waiting, and call transfer. CCXML enables applications to offer users the ability to place outbound calls, conditionally answer calls, and to initiate or receive outbound communications such as another call.


The Speech Recognition Grammar Specification (SRGS) and the Semantic Interpretation for Speech Recognition standard support the development of speech grammars to be used in voice applications. Grammars are a central component to voice applications which define the set of words or word combinations that are recognized by an application.

XHTML + Voice (X+V)

IBM, Motorola, and Opera have drafted a proposal for combining VoiceXML, which allows navigation of Web pages through the use of voice commands, with XHTML, a mark-up language used to create Web pages. This proposal, officially named XHTML + Voice, is also known as X+V. Several prototype multimodal applications have been developed using X+V and XHTML modules.

Aural Style Sheets

The CSS 2.0 specification make provisions for people with visual impairments through Aural Style Sheets. Using a style sheet, an aural CSS-capable browser reads the text of a Web page over the computer’s speakers. Aural style sheets allow a designer to set the volume and voice stress of various HTML elements, as well as the length of pauses and the rate of speech.

Note – the definitive source on all of the above standards is the W3C.

Voice over Internet Protocol (VoIP)

VoIP refers to a set of standards that can be used to transmit telephone calls over the Internet and other packet-switched networks:

  • SIP: Session Initiation Protocol
  • RTP: Real-time Transport Protocol
  • IAX: Inter-Asterisk eXchange protocol
  • Skype Protocol
  • H.323