Sets of telecommunications protocols and interfaces defined by CCITT (now ITU-T) Recommendations. Note: Some of the more common V. -series Recommendations are:V. 21: A CCITT Recommendation for modem communications over standard commercially available lines at 300 b/s. This protocol is generally not used in the United States. V. 22bis: A CCITT Recommendation for modem communications over standard commercially available voice-grade channels at 2,400 b/s and below. V. 32: A CCITT Recommendation for modem communications over standard commercially available voice-grade channels at 9. 6 kb/s and below. V. 32bis: A CCITT Recommendation for modem communication over standard commercially available voice-grade channels at 14. 4 kb/s and below. V. 34: An ITU-T Recommendation for modem communication over standard commercially available voice-grade channels at 28. 8 kb/s and below. V. 42: A CCITT Recommendation for error correction on modem communications. V. 42bis: A CCITT Recommendation for data compression on a modem circuit. V. FAST: A new CCITT Recommendation for high-speed modems currently under development.