V.32

V.32 is an ITU standard from the 1980s for synchronous data transmission via modems. V.32 operates in duplex with 4.8 kbit/s and 9.6 kbit/s and Automatic Fallback( AFB), which reduces the data rate in poor transmission conditions. Switching back to higher data rates is not possible.

To improve transmission, V.32 uses trellis coding, in which four data bits are transmitted representing five bits of information. The fifth bit is obtained from the four data bits. The duplex channel is obtained by filtering. Furthermore, V.32 works with error correction and compresses the data transmission by means of Time Compressing Multiplexing( TCM).