Timewave DSP-232, Руководство по эксплуатации

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Chapter 8 ASCII and Baudot Operation
Chapter 8
ASCII and BAUDOT Operation
Overview
ASCII, the American Standard Code for Information Interchange (pronounced as-kee), has been around for nearly
30 years. ASCII is a 7-bit code and was designed to overcome the limitations of the Baudot character set by
including both upper and lowercase letters, numbers, all punctuation characters as well as many computer control
codes. However, by using a longer digital “word,” the probability of receiving errors in ASCII is somewhat higher
than Baudot because of the time element—noise has a greater chance of interfering with the longer word than a
shorter one. For these reasons, ASCII is not used widely on the HF amateur bands as Baudot; some commercial and
military HF stations use ASCII.
Baudot has been around for many years. The 5-bit Baudot/Murray code was the basis of the Western Union Telex
service and Baudot RTTY (Radio TeleTYpe) is still widely used on the HF amateur bands. The Baudot character set
contains the upper-case letters, the numbers 0-9, and some common punctuation characters. Because Baudot has
only five bits, it’s less prone to errors than 7-bit ASCII because of signal timing considerations. The DSP’ provides
Baudot RTTY at all the standard speeds in use today, including all commercial speeds up to 300 bauds; there’s also
the
XBAUD command for use with non-standard baud rates.
Before proceeding with the rest of this chapter, review the following commands that are directly applicable to the
Baudot and ASCII modes:
AAB
,
ABAUD
,
ACRDISP
,
ACRTTY
,
ALFDISP
,
ALFRTTY
,
ATXRTTY
,
CODE
,
CRADD , CWID, DIDDLE , EAS , HEREIS, LOCK, MARSDISP , NUMS, RBAUD , RECEIVE, RCVE,
RXREV , TXREV , USOS, WIDESHIFT , WORDOUT , WRU , XBAUD, and XMIT.
Operating ASCII and Baudot
ASCII and Baudot operation are virtually identical. Those commands which pertain just to Baudot will be noted in
parenthesis.
Setting Up for ASCII
(If you're using an AEA program, follow the instructions in the program's manual to set up and use ASCII.)
To use the ASCII mode, simply enter ASCII (or AS ) at the
cmd:
prompt. The DSP responds by displaying the
previous mode it was in, then its new mode:
cmd:
AS
Opmode was
(
previous mode
)
Opmode now AScii
cmd:
Look at your DSP’s front panel to verify that you're in the ASCII mode—an ‘E’ should be lit in the Mode display.
You can choose the appropriate modem number at this point using the MODEM command. For a list of available
modems use the DIR command.
September, 05 8-1