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X.21�:�Interface between Data Terminal Equipment and Data Circuit-terminating Equipment for synchronous operation on public data networks �

Recommendation X.21

In force components
Number
 Title Status
X.21 (09/92)
� 		Interface between Data Terminal Equipment and Data Circuit-terminating Equipment for synchronous operation on public data networks � In force
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Superseded and Withdrawn components
Number
 Title Status
X.21 (11/88)
� 		Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks � Superseded
X.21 (1988) Corrigendum 1 (07/89)
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Cor.1 to X.3 (1988), X.21 (1988), X.25 (1988), X.28 (1988), I.461/X.30 (1988), I.462/X.31 (1988) and X.32 (1988) were published in a common covering note in June 1990 		Superseded

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