V.FC
<communications, protocol> A serial line protocol supported by some
modems. Uses symbol rates of 2400, 2800, 3000, >3200 and 3429 and up to 28800
baud.
V.34 modems will also support V.FC if the manufacturer currently supports V.FC.
The first V.FC modems were shipped in November 1993 and there have been many
thousands sold. There will probably be in excess of a million V.FC modems
installed by the end of 1994.
V.FC was intended to take some of the techniques being proposed for V.34 and put
them into a real modem that people could use. This also gave a lot of people the
opportunity to try out 28.8 kilobit per second operation for the first time.
There was never any intention from Hayes or Rockwell (who worked together for
two years on V.FC) that V.FC would be compatible with V.34 - even if they had
wanted it, others would have made sure it didn't happen! In fact, they made the
start-up deliberately different from V.34 so that it would be easy to
distinguish between the two and easier to make dual-mode V.FC/V.34 modems.
V.FC is quite different from V.34. Most of the signal-processing algorithms,
whilst based on the same theory, are implemented in different ways. V.34 has
some extra things like a secondary channel and a special mode for 28.8 kilobit
per second fax.
The Rockwell V.FC implementation uses a single-chip mask-programmed DSP for all
the signal processing functions. You can also buy a modem controller chip from
Rockwell to go with it which implements AT commands, error-control and
compression. Hayes made their own controller using the Motorola 68302 processor.
When it comes to an upgrade from V.FC to V.34 you have to have a new, masked DSP
chip and new controller firmware to implement all the V.34-specific features.
This means that Rockwell-DSP based modems must be returned to the manufacturer
for upgrade. Upgraded modems will talk to either V.FC or V.34 modems.
Nearby terms:
VESA Local Bus « V.FAST « VFAT « V.FC » vg »
VGA » VGQF
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