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V.29 is an ITU standard for half-duplex fax transmissions. It uses quadrature amplitude modulation (QAM) with 45-degree and 90-degree phase positions.

At a step rate of 2,400 baud and a transmission of four bits per step, V.29 achieves a transmission rate of 9.6 kbit/s with 8-phase phase shift keying (PSK).

Phase star of V.29

Phase star of V.29

The procedure is used with fax and switches itself in bad transmission conditions by means of Automatic Fallback (AFB) the transmission rate down to lower values.

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Englisch: V.29
Updated at: 26.10.2011
#Words: 116
Translations: DE