# Recommendation X.211 (11/1988): Physical service definition of open systems interconnection for CCITT applications

> superseded recommendation/international standard from the International Telecommunication Union

**Wikidata**: [Q27051509](https://www.wikidata.org/wiki/Q27051509)  
**Source**: https://4ort.xyz/entity/recommendation-x-211-11-1988-physical-service-definition-of-open-systems-interconnection-for-ccitt-applications