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6.4
MODULATION PROTOCOLS
Using Multi-Protocol Auto-Answer
The multi-protocol auto-answer feature allows auto-answer of incoming
calls from modems using any of the following protocols: V.34, V.FC,
V.32bis, V.32, V.22bis, V.22 (1200 bps only), V.21, V.23 half-duplex, Bell
212A, and Bell 103.
To enable this feature for V.23 half-duplex connections, set :T2
NOTE
to a value greater than 0. We recommend setting :T2=20 when
falling back to a V.23 half-duplex connection.
V.34 and V.FC
Basically, V.34 is the new ITU-T standard that formalizes the temporary
V.FC (V.fast Class) protocol. It has all the features of our V.FC modems,
plus the additional commands described in Appendix A. You can enjoy the
same 28,800 bps connect speeds, high data integrity, and throughputs up
to 115,200 bps.
One obvious improvement is "handshaking" between V.34 modems.
Connection negotiation will take about 5 seconds instead of up to 15
seconds and will use a few new tones. V.34 includes the new V.8
handshake standard, and adds line probing and fast negotiation between
two modems that support it. If the other modem does not include V.8,
your modem will proceed with the previous negotiation methods. Expect
these faster negotiations as V.34 modems become common.
You should also see better adaptations to phone lines. In V.34
connections, our modems stay in that modulation from 2,400 through
28,800 bps. The V.FC range is 14,000 through 28,800 bps. If line
conditions require fallback or permit fall-forward, two V.34 modems can
perform either easily.
Finally, while not all V.34 modems support V.FC connections, ours do.
That means you can expect continued high-speed connections to over 1
million V.FC modems from over 120 vendors. By default, your modem
will start a negotiation at V.34 and if it can't get one, connect at V.FC,
V.32bis and V.32 in that order - permitting the highest speed connections
with other modems.
CSMIM-T1 Hardware Installation Guide
Modulation Protocols
6-7
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