# Recommendation U.15 (11/1988): Interworking rules for international signalling systems according to Recommendations U.1, U.11 and U.12

> superseded recommendation/international standard from the International Telecommunication Union

**Wikidata**: [Q27051469](https://www.wikidata.org/wiki/Q27051469)  
**Source**: https://4ort.xyz/entity/recommendation-u-15-11-1988-interworking-rules-for-international-signalling-systems-according-to-recommendations-u-1-u-11-and-u-12