private signalling system 1 (PSS1)

The International Standards Organization(ISO) had developed a standard for QSIG under the name PSS1 (Private Signaling System 1) at the same time as the European Computer Manufacturers Association ( ECMA).

The PSS1 standard was renamed ISO-QSIG (Q-Interface Signalling Protocol) as part of the harmonization process. Both bodies, the European Telecommunications Standards Institute( ETSI) and the International Standards Organization (ISO), have advanced their standards in recent years, taking into account the current status of the other organization in their further development.

The PSS1 standard describes a signaling protocol for communication between private PBXs from different manufacturers.