# Recommendation X.1 (11/1988): International user classes of service in public data networks and integrated services digital networks (ISDNs)

> superseded recommendation/international standard from the International Telecommunication Union

**Wikidata**: [Q26985474](https://www.wikidata.org/wiki/Q26985474)  
**Source**: https://4ort.xyz/entity/recommendation-x-1-11-1988-international-user-classes-of-service-in-public-data-networks-and-integrated-services-digital-networks-isdns-