INTERNATIONAL  TELECOMMUNICATION  UNION

		     ITU-T RECOMMENDATION SUMMARY


Rec. No. : Q.83.1

Title :	Stage 2 description for call completion supplementary services

Study Group : XI - Switching and Signalling

Version : Revised

Date of adoption : 1991

Notes :	


			CALL WAITING (CW)

Recommendation Q.83.1 defines the stage 2 of the integrated services 
digital network (ISDN) as provided for the call waiting (CW) 
supplementary service. Stage 2 identifies the functional capabilities 
and the information flows needed to support the service description. 
The stage 2 description also identifies user operations not directly 
associated with a call (see Rec. I.130).

Recommendation Q.83.1 is specified according to the methodology 
specified in Recommendation Q.65 [2].

Recommendation Q.83.1 does not formally describe the relationship 
between this supplementary service and the basic call but, where 
possible, the information is included for guidance.

In addition, Recommendation Q.83.1 does not specify the requirements 
where the service is provided to the user via a private ISDN. This 
Recommendation does not specify the requirements for the allocation of 
defined functional entities within a private ISDN; it does however 
define which functional entities may be allocated to a private ISDN.

Recommendation Q.83.1 does not specify the additional requirements 
where the service is provided to the user via a telecommunications 
network that is not an ISDN.

The CW supplementary service permits a subscriber to be notified of an 
incoming call (as per basic call procedures) with an indication that 
no interface information channel is available. The user then has the 
choice of accepting, rejecting or ignoring the waiting call (as per 
basic call procedures).

The CW supplementary service is considered meaningful when applied to 
the telephony teleservice and the speech and 3.1 kHz audio bearer 
services. Furthermore, it may also be meaningful when applied to 
other services.

Recommendation Q.83.1 is applicable to the stage 3 Recommendations 
for the ISDN CW supplementary service. The term "stage 3" is also 
defined in Recommendation I.130.



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