The ITU-T Recommendation for full-duplex (FDX) asynchronous dial-up modems operating over the public switched telephone network (PSTN) at transmission rates up to 9600 bps, with the capability to fall back to 4800 bps, over a 4-kHz analog voice grade channel. See also analog, asynchronous, channel, FDX, modem, PSTN, transmission rate, and voice grade.
An ITU standard (1984) for asynchronous and synchronous 4,800 and 9,600 bps full-duplex analog modems using trellis-coded modulation (TCM) modulation over dial-up or two-wire leased lines. TCM encoding may be optionally added. V.32 uses echo cancellation to achieve full-duplex transmission.