V.42bis

V.42bis

(communications, standard)
An extension of the ITU-T V.42 standard modem protocol to included compression using a Lempel-Ziv related technique, which detects frequently occurring character strings and replaces them with tokens. This is similar to the Unix compress utility. Typical compression for text is 50% or better; with nearly 20% gain from synchronous conversion this gives reduces transmission time by almost 60%.

V.42bis

An ITU standard (1989) for analog modem data compression. It uses the BTLZ technique to achieve up to a 4:1 ratio. V.42bis implies the V.42 error checking protocol.
References in periodicals archive ?
Other features include V.42 and MNP2-4 error correction, V.42bis and MNP5 data compression, standard serial or parallel interface, line-in-use and parallel phone detection, fast connect modes and caller ID.
The company will further enhance its V.92 software suite with the addition of V.44 data compression capability, which typically improves data compression by some 20% to 60% over the V.42bis compression scheme employed in V.90--and as much as 200% for certain highly-compressible files.
The modem hardware provides V.42 error correction for 100 percent error-free transmissions and V.42bis data compression yielding asynchronous throughputs up to 115 Kbps, which are four times faster than 28.8 Kbps V.34 alone (depending on file content).
The MT1932BL provides synchronous or asynchronous operation over dedicated or dial-up phone lines, with V.42 error correction in asynchronous mode for 100 percent error-free data and V.42bis "4-to-1" data compression for effective throughputs up to 76.8K bps (depending on file content).
The 9.6/FAX modems combine 9,600 bps (V.32) data speeds and 38,400 bps (V.42bis) throughput with Group III FAX compatibility.
The LanFast network modem contains an integral, fully compatible V.32bis, V.42bis, 14.4K bps modem.