Q

See: Quality Factor

Q.931

A telecom call processing signaling protocol that is used in telephone communication systems. The Q.931 protocol defines the messages and formats are control messages that are created by the end communication device. Some of the common information contained in Q.931 messages include call setup and tear down messages, called and calling party telephone numbers, and other access control signaling messages.

This diagram shows the basic structure of a Q.931 signaling message. The examples in this diagram show that Q.931 messages are used to provide information to setup, maintain, and tear down communication connections. Although Q.931 is ISDN (digital) related, the signaling message structure is also used for some analog communication systems.

A 931 Message Structure

QA

See: Quality Assurance

QAM

See: Quadrature Amplitude Modulation

QBE

See: Query By Example

QBone

See: Quality Of Service Backbone

QC

See: Quality Control

QoS

See: Quality Of Service

QPSK

See: Quadrature Phase Shift Keying

QSIG

QSIG is a peer-to-peer signaling standard that enables call setup between voice-enabled equipment made by different manufacturers. QSIG is also known as Private Signaling System No. 1 (PSS1) and falls under the auspices of both the European Telecommunications Standards Institute (ETSI) and the International Standards Organization (ISO). In addition to QSIG s ability to set up a basic call, supplementary QSIG services specify how calling features, such as line forwarding, call transfer, call forwarding, and many others, can work across different vendors platforms. QSIG grew out of...