Q series - technical definition

The series of ITU-T Recommendations specifying protocols relating to switching and signaling. See Table Q-1 of selected Q-series Recommendations. For a full listing of ITU-T Recommendations, see the contact information in Appendix A.

Table Q-1: Selected ITU-T Q-Series Recommendations

Recommendation	Description
Q.20	Comparative advantages of in-band and out-of-band signaling systems
Q.21	Systems recommended for out-band signaling
Q.22	Frequencies to be used for in-band signaling
Q.23	Technical features of push-button telephone sets
Q.71	ISDN circuit mode switched bearer services
Q.700	Introduction to CCITT Signaling System No. 7 (SS7)
Q.716	SS7 - Signaling connection control part (SCCP) performance
Q.721	Functional description of SS7Telephone User Part (TUP)
Q.824.1	ISDN basic and primary rate access
Q.824.2	ISDN supplementary services
Q.824.3	ISDN optional user facilities
Q.824.4	ISDN teleservices
Q.921	ISDN user-network interface - Data link layer specification
Q.931	ISDN user-network interface layer 3 specification for basic call control
Q.2763	SS7 B-ISDN User Part (B-ISUP) - Formats and codes
Q.2764	SS7 B-ISDN User Part (B-ISUP) - Basic call procedures