# Recommendation I.604 (11/1988): Application of maintenance principles to ISDN primary rate accesses

> superseded recommendation/international standard from the International Telecommunication Union

**Wikidata**: [Q27051426](https://www.wikidata.org/wiki/Q27051426)  
**Source**: https://4ort.xyz/entity/recommendation-i-604-11-1988-application-of-maintenance-principles-to-isdn-primary-rate-accesses