TECHNICAL BULLETIN #99 - Rev 1.00 (5/13/96)

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TITLE   : Why Are 144 & 288 Baud Rates Omitted from 2.01?
PRODUCT : PROCOMM PLUS 2.01 (DOS)
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This document explains why 14400 and 28800 baud rates were omitted in 
PROCOMM PLUS.

SPLIT-BAUD, DATA COMPRESSING MODEMS

Your high-speed modem uses "split-baud" technology to operate at two baud
rates.  The first baud rate is the speed your modem negotiates when it
connects with another modem and is known as the DCE (Data Communications
Equipment) speed.  The second baud rate is the speed between your modem and
your computer, known as the DTE (Data Terminal Equipment) speed.  The DTE
speed is the rate you select in PROCOMM PLUS Dialing Directory and Current
Setup.

In addition, your modem supports data compression, such as V.42bis' "4 to 1" 
data compression.  In simpler terms, this means your modem could potentially 
compress 4 bytes of data to only 1 byte.  This technology, in conjunction
with "split-baud", allows your modem to receive data from your PC at up to
four times the DCE speed, then buffer, compress, and send the data to another
modem.  The receiving modem will buffer, uncompress, and send the data to
its PC at a similarly high rate.


|-------|  57,600  |-------|     14,400     |--------|  57,600  |--------|
| Local |   baud   | Local |      baud      | Remote |   baud   | Remote |
|  PC   |<-------->| Modem |<-------------->| Modem  |<-------->|  PC    |
| (DTE) |          | (DCE) |   PHONE LINE   | (DCE)  |          | (DTE)  |
|-------|          |-------|                |--------|          |--------|
           

If you set the DTE speed less than four times the DCE speed, data will not
be sent to your modem fast enough for it to compress the data and your file
transfer rates will suffer.  Instead, set the DTE speed to four times the
maximum DCE speed of your modem: 57600 baud for 14400 baud modems and
115200 baud for 28800 baud modems.  The designers of PROCOMM PLUS omitted
the 14400 and 28800 baud rates so that you would not mistakenly reduce your
file transfer rates.

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