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Subject:Re: Gentlepersons, set your modems! From:Matt Ion <mion -at- NEXTLEVEL -dot- COM> Date:Fri, 8 Sep 1995 03:43:59 PDT
On Fri, 8 Sep 1995 02:47:50 -0400 you wrote:
>In answer to the question about which preposition to use after "set":
>When I set my modem for 14.4 kbaud compressed transmission, I am setting it
>to 9600 baud. This only works if my COM port is set at 19.2 kbaud. ...RM
While your statement may be gramatically correct, Richard, technically it's
far off base (at least, if it's actually saying what I *think* it's saying,
it's far off base). I'd expect better from a technical writer.
"Baud" refers to the frequency of signal with which modems talk to each other.
All high-speed modems communicate at 4800 baud. Higher BPS (bits per second)
rates are achieved through modulation and phase-shifting of that signal.
When you set your modem for 14.4kbps transmission, you are setting it for 4800
baud, 14,400bps transfer. With compression, actual throughput may be higher
(whic is why port speed is locked higher than the connect speed), but the two
modems will still only be communicating with each other at 14.4kbps.
If transferring a lot of compressed files (including GIF and JPG images),
on-board compression such as MNP5 and V42.bis offer little improvement. On
highly compressable files (such as text files, for example), however, V.42bis
can provide up to 4:1 compression, for an effective throughput of up to
57.6kbps (theoretically, at least). However, the modems are still only
talking to each other at 14.4kbps. The port speed should be higher because
once the receiving modem decompresses that compressed data, there's going to
be a lot more of it (up to four times more) to dump through into the serial
port.
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