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Q.521�:�Digital exchange functions �

Recommendation Q.521

In force components
Number
 Title Status
Q.521 (03/93)
� 		Digital exchange functions � In force
�
�
Superseded and Withdrawn components
Number
 Title Status
Q.521 (11/88)
� 		Exchange functions �
Replaces Q.503 (1984) and Q.513 (1984) 		Superseded

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