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Q.120-Q.139�:�Specifications of signalling system No. 4 �

Recommendation Q.120-Q.139

In force components
Number
 Title Status
Q.120-Q.139 (11/88)
� 		Specifications of signalling system No. 4 �
Initially published in Blue Book Fascicle VI.2 (1988). Available now in electronic format only 		In force

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