# Recommendation X.21bis (11/1988): Use on public data networks of Data Terminal Equipment (DTE) which is designed for interfacing to synchronous V-Series modems

> recommendation/international standard from the International Telecommunication Union

**Wikidata**: [Q26985484](https://www.wikidata.org/wiki/Q26985484)  
**Source**: https://4ort.xyz/entity/recommendation-x-21bis-11-1988-use-on-public-data-networks-of-data-terminal-equipment-dte-which-is-designed-for-interfacing-to-synchronous-v-series-modems