CCITT standard for modem communications at 14,400bps with automatic fallback to 12,000, 9600, 7200 and 4800bps. As line quality improves communications speed can also be increased to the next higher rate.
An ITU-T standard that extends the V.32 connection range: 4800, 7200, 9600, 12,000, and 14,400 bps. V.32 bis modems fall back to the next lower speed when line quality is impaired, fall back further as necessary, and also fall forward (switch back up) when line conditions improve. See online fall back/fall forward.