INTERNATIONAL  TELECOMMUNICATION  UNION

		     ITU-T RECOMMENDATION SUMMARY


Rec. No. : Q.731.1

Title :	Stage 3 description for number identification supplementary 
	services using signalling system No. 7

Study Group : XI - Switching and Signalling

Version : New

Date of adoption : 1992

Notes :	


			DIRECT-DIALLING-IN (DDI)

Direct-Dialling-In (DDI) enables a user to call directly another user 
on an ISPBX or other private system without attendant intervention, 
the DDI digit(s) being the least significant digit(s) of the called 
ISDN number.

The stage 1 definition of DDI is to be found in Recommendation I.251. 
The stage 2 description is included in Recommendation Q.81.1. This 
stage 3 description of DDI compliments the ISDN User Part (ISUP) 
protocol as defined in Recommendations Q.761 to Q.764 and Q.766.



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