# Recommendation I.231.3 (11/1988): Circuit-mode bearer service categories : Circuit-mode 64 kbit/s, 8 kHz structured bearer service usable for 3.1 kHz audio information transfer

> recommendation/international standard from the International Telecommunication Union

**Wikidata**: [Q27051389](https://www.wikidata.org/wiki/Q27051389)  
**Source**: https://4ort.xyz/entity/recommendation-i-231-3-11-1988-circuit-mode-bearer-service-categories-circuit-mode-64-kbit-s-8-khz-structured-bearer-service-usable-for-3-1-khz-audio-information-transfer