Proper noun
Q.931
English Wikipedia has an article on:Q.931Wikipedia
An ISDN connection protocol somewhat similar to TCP.
It was introduced before the Q.931 standard was finalised by the International Community. Source: Internet
Q.931 is the name of the CCITT document that describes the agreed signalling format for International ISDN. Source: Internet
Sample call The following is an example of a Primary Rate (PRI) ISDN call showing the Q.921 LAPD and the Q.931 /Network message intermixed (i.e. exactly what was exchanged on the D-channel). Source: Internet
In common use, ISDN is often limited to usage to Q.931 and related protocols, which are a set of signaling protocols establishing and breaking circuit-switched connections, and for advanced calling features for the user. Source: Internet
Individual service providers may publish their own documentation that details further messages that will be transported in addition to Q.931 messages. Source: Internet
Signaling channel The signaling channel (D) uses Q.931 for signaling with the other side of the link. Source: Internet