# Recommendation I.231.5 (11/1988): Circuit-mode bearer service categories : Circuit-mode 2 x 64 kbit/s unrestricted, 8 kHz structured bearer service

> recommendation/international standard from the International Telecommunication Union

**Wikidata**: [Q27051392](https://www.wikidata.org/wiki/Q27051392)  
**Source**: https://4ort.xyz/entity/recommendation-i-231-5-11-1988-circuit-mode-bearer-service-categories-circuit-mode-2-x-64-kbit-s-unrestricted-8-khz-structured-bearer-service