# Recommendation U.12 (11/1988): Terminal and transit control signalling system for telex and similar services on international circuits (type D signalling)

> superseded recommendation/international standard from the International Telecommunication Union

**Wikidata**: [Q26985466](https://www.wikidata.org/wiki/Q26985466)  
**Source**: https://4ort.xyz/entity/recommendation-u-12-11-1988-terminal-and-transit-control-signalling-system-for-telex-and-similar-services-on-international-circuits-type-d-signalling-