1 Introduction and Description

V.90 Support/Functions

V.90 is the ITU designation for what formerly was called V.pcm. V.90 replaces K56flex and other proprietary solutions for PCM connections. Dual-mode client modem code will be important until all central-site digital modems are upgraded to V.90 and all interoperability problems are resolved. Until that time, the Dual-mode client code provides reliable connections in K56flex mode to the central-site modems currently deployed. V.90 functions/features include:

V.90/K56flex A-law and µ-law support

New downstream data rates (S-Register S38)

Optional V.8bis sequence

V.90 Mode Selection (S-Register S109) support

Auto-rate speeds to 50,666 (downstream) support

Automatic adapting to digital loss and robbed-bit signaling

New V.90 rate result codes

Downstream Rates

Where K56flex provided rates of 32,000 to 56,000 in 2,000 bps increments, V.90 provides rates of 28,000 to 56,000 bps in increments of 1,333 bps.

Upstream Data Rates

Upstream V.90 data rates are 4800 to 33600 bps in 2400 bps increments.

Optional V.8bis Sequence

The V.8bis sequence that precedes K56flex connections is optional for V.90. Dual-mode servers indicate this capability using V.8bis. Dual- mode clients complete the V.8bis exchange and then proceed to either the K56flex mode or V.90 mode. V.90-only clients can skip the V.8bis exchange as a way to shorten the startup time.

Auto-rate Speeds

Auto-rate speeds to 50,666 Kbps are supported for downstream transfers.

MT5634ZPX-PCI

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Multi-Tech Systems MT5634ZPX-PCI Support/Functions, Downstream Rates, Upstream Data Rates, Optional V.8bis Sequence