Q.SIG

Q Signaling, a signaling standard for PBX interoperability used in the United States and Europe.

Q.SIG is an ISDN-based protocol developed for networking different enterprise switching systems together and providing additional supplementary services for feature transparency.

Q.SIG has its origins in standards defined originally by the European Computer Manufacturing Association (ECMA) dating back to the mid-1980s. In the early 1990s, these standards were submitted to the International Organisation for Standardisation (ISO) for globalisation, and after certain adaptation to other country's requirements, were issued in 1994 as a global standard. Since then, many additional features and changes have been adopted. ECMA has also taken on work to harmonize their versions with the ISO changes.

Q.SIG is valuable at a network site when an enterprise finds itself with PBX systems from differing vendors. Q.SIG can also be useful as a means of connecting different functional units (e.g., PBX and financial turret) to save expenses by sharing public network interfaces.

Q.SIG will likely never rival each vendor's private network protocols, but it does provide an option for a higher level of integration than that of the traditional choices.