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Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks

superseded recommendation/international standard from the International Telecommunication Union
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Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks

Summary

Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks is an ITU-T recommendation version[1].

Key Facts

  • Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks's instance of is recorded as Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks — instance of (P31): ITU-T recommendation version[2].
  • Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks's publisher is recorded as Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks — publisher (P123): ITU Telecommunication Standardization Sector[3].
  • Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks's edition number is recorded as 11/1988[4].
  • Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks's language of work or name is recorded as Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks — language of work or name (P407): English[5].
  • Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks's publication date is recorded as +1988-11-25T00:00:00Z[6].
  • Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks's edition or translation of is recorded as Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks — edition or translation of (P629): X.21[7].
  • Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks's official website is recorded as https://www.itu.int/rec/T-REC-X.21-198811-S/en[8].
  • Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks's work available at URL is recorded as https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-X.21-198811-S!!PDF-E&type=items[9].
  • Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks's number of pages is recorded as {'unit': '1', 'amount': '+56'}[10].
  • Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks's standards body is recorded as Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks — standards body (P1462): International Telecommunication Union[11].
  • Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks's title is recorded as Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks[12].
  • Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks's ITU-T Recommendation is recorded as X.21 (11/1988)[13].

Body

Authorship and Creation

Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks's publisher is recorded as Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks — publisher (P123): ITU Telecommunication Standardization Sector[3].

Publication

Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks's publication date is recorded as +1988-11-25T00:00:00Z[6]. Its language of work or name is recorded as Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks — language of work or name (P407): English[5].

References

Programmatic citations — every numbered marker resolves to a verifiable graph row below.

Direct Wikidata claims

  1. [2] ↑ . wikidata.org.
  2. [3] ↑ . wikidata.org.
  3. [4] ↑ . wikidata.org.
  4. [5] ↑ . wikidata.org.
  5. [6] ↑ . wikidata.org.
  6. [7] ↑ . wikidata.org.
  7. [8] ↑ . wikidata.org.
  8. [9] ↑ . wikidata.org.
  9. [10] ↑ . wikidata.org.
  10. [11] ↑ . wikidata.org.
  11. [12] ↑ . wikidata.org.
  12. [13] ↑ . wikidata.org.

Class ancestry

  1. [1] ↑ . Wikidata. wikidata.org.

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Use these citations when quoting this entity in research, articles, AI prompts, or wherever provenance matters. We aggregate Wikidata + Wikipedia + authoritative open-data sources; the stitched, scored, cross-referenced view is what 4ort.xyz contributes.

APA 4ort.xyz Knowledge Graph. (2026). Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks. Retrieved May 3, 2026, from https://4ort.xyz/entity/recommendation-x-21-11-1988-interface-between-data-terminal-equipment-dte-and-data-circuit-terminating-equipment-dce-for-synchronous-operation-on-public-data-networks
MLA “Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks.” 4ort.xyz Knowledge Graph, 4ort.xyz, 3 May. 2026, https://4ort.xyz/entity/recommendation-x-21-11-1988-interface-between-data-terminal-equipment-dte-and-data-circuit-terminating-equipment-dce-for-synchronous-operation-on-public-data-networks.
BibTeX @misc{4ortxyz_recommendation-x-21-11-1988-interface-between-data-terminal-equipment-dte-and-data-circuit-terminating-equipment-dce-for-synchronous-operation-on-public-data-networks_2026, author = {{4ort.xyz Knowledge Graph}}, title = {{Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks}}, year = {2026}, url = {https://4ort.xyz/entity/recommendation-x-21-11-1988-interface-between-data-terminal-equipment-dte-and-data-circuit-terminating-equipment-dce-for-synchronous-operation-on-public-data-networks}, note = {Accessed: 2026-05-03}}
LLM prompt According to 4ort.xyz Knowledge Graph (aggregator of Wikidata, Wikipedia, and authoritative open-data sources): Recommendation X.21 (11/1988): Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks — https://4ort.xyz/entity/recommendation-x-21-11-1988-interface-between-data-terminal-equipment-dte-and-data-circuit-terminating-equipment-dce-for-synchronous-operation-on-public-data-networks (retrieved 2026-05-03)

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