ORIGINAL MESSAGE:
On Mon, 11 Feb 2013 10:10:02 -0500, you wrote:
>The space character is in both "character sets", i.e. LTRS and FIGS.
>It shouldn't be necessary to send a FIGS character after a space
>(or LTRS before) when sending a space delimited series of
>numbers. UOS would seem to break this - i.e. assume
>LTRS after a space - but it clearly doesn't.
REPLY:
If reception was perfect, i.e. no garbled characters, then USOS would not
be necessary. In fact, with wired TTY it isn't used at all. Only with radio
TTY is it needed.
The idea behind it is that in ordinary conversation, letters are much more
common than numbers and normally a LTRS character is not needed nor is it
ever sent. The problem is that occasionally a number is sent and it should
normally be followed by a LTRS character once the message goes back to
letters again. IF the LTRS character is garbled, then the entire message
that follows will be in the wrong shift and the entire message will be
gibberish. USOS prevents this by sending a LTRS character every time it
detects a space, thus resetting things back to "normal".
It does slow things down since the extra LTRS character does require 167
milliseconds every time it is sent, but generally the tradeoff is worth it,
especially under conditions of QRM and/or QRN. As I say, when transmitting
over wires there is no QRM and/or QRN and USOS is not needed.
Make sense?
Bill, W6WRT
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