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Collaboration, Voice & AV · Advanced

Q Signaling (QSIG)

An ISDN-based inter-PBX signaling protocol that passes features such as calling name and message waiting between systems.

Definition

QSIG, standardized by ECMA and ISO, runs on PRI or BRI D channels and adds supplementary services beyond basic Q.931 call setup, including name identification, call diversion, path replacement and message waiting indication. It is commonly used to integrate a legacy PBX with CUCM or a third-party voicemail system during migration. CUCM supports QSIG over MGCP PRI and tunneled QSIG over H.323 or SIP trunks.

Example

CUCM and a legacy PBX share a QSIG PRI so that a user on either side sees the caller's name and receives MWI.

Exam tip

Choose QSIG when a scenario requires feature transparency between a PBX and CUCM over a TDM trunk.

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