11 Dec
2004
11 Dec
'04
9:04 a.m.
Fred Cisin <cisin(a)xenosoft.com> wrote:
Do you know of any timesharing host or BBS that is
compatible with TTY?
Sure, any PDP-11 or VAX UNIX timesharing host with a Bell 103 modem
attached to one of its RS-232 ports will happily accept calls from an
ASR33 TTY.
It's a pity that the deaf TTYs are 5-bit rather than ASCII. The reason
for my question had to do with my campaign to get the few people I care
about to switch from PeeCees to timesharing computing, i.e., instead of
using a PeeCee, paying for Internet service, etc., get an account on my
VAX and dial into it from a Teletype. One of the problems is of course
that no one has Teletypes any more. I was wondering if the deaf ones
could be used, as in the current horrible state of the world it seems
like Teletypes are now only used by the disabled, rather than by 100% bodily
abled people who are more intelligent than the masses and want to use
timesharing UNIX (or VMS or RSX or TENEX or ...) instead of a pee sea.
BTW, has there ever been a Teletype model that did 300 baud instead of 110?
Perhaps Model 35 or 37? My Courier V.Everything modems are great, and
they can go down to Bell 103 or V.21, but to my knowledge they do not have
an asynchronous pass-thru mode between the RS-232 TxD/RxD lines and the
Bell 103 FSK modulator/demodulator, it always has to go through the modem's
internal buffers, which requires it to know the baud rate, and as a result
it can only operate at 300 baud with Bell 103 / V.21, even though this
modulation scheme is in fact asynchronous and baud rate-oblivious for the
range 0-300 baud. The end result is that they can't answer 110 baud calls
from ASR33s. Bummer.
MS
11 Dec
11 Dec
11:24 a.m.
On Sat, 11 Dec 2004, Michael Sokolov wrote:
so,...
the ASR33 TTY is Bell 103 at 300 baud?
"MODERN" modems that will do Bell 103, will often only do it at 300 baud.
... and if you take that Bell 103 modem off, and replace it with a V.18
modem, then the TDDs can connect at 45.45 baud.
Do you know of
any timesharing host or BBS that is compatible with TTY?
Sure, any PDP-11 or VAX
UNIX timesharing host with a Bell 103 modem
attached to one of its RS-232 ports will happily accept calls from an
ASR33 TTY. It's a pity that the deaf TTYs are 5-bit rather
than ASCII. The reason
surely SOMEBODY knows how to write a look-up table program
to translate!
(it's substantially less than 1K)
for my question had to do with my campaign to get the
few people I care
about to switch from PeeCees to timesharing computing, i.e., instead of
using a PeeCee, paying for Internet service, etc., get an account on my
VAX and dial into it from a Teletype. One of the problems is of course
that no one has Teletypes any more. I was wondering if the deaf ones
could be used, as in the current horrible state of the world it seems
like Teletypes are now only used by the disabled, rather than by 100% bodily
abled people who are more intelligent than the masses and want to use
timesharing UNIX (or VMS or RSX or TENEX or ...) instead of a pee sea.
The cheapest terminal that you can get is an obsolete PC.
Come to my neighborhood during the sidewalk/bulk pickup days!
TDDs are more expensive, and do not have a 24 x 80 screen.
They typically have a single line display, and sometimes an
adding machine width printer.
For what kind of applications would you consider that interface connected
to a timesharing system to be more usable than a personal computer,
or a 24 x 80 screen terminal?
11:54 a.m.
On Sat, 11 Dec 2004, Fred Cisin wrote:
ASR-33's and their ilk are ASCII and 110 baud (43's do 300
I think).
The TTY-for-the-deaf tech is based upon older ITA2 (aka "baudot"
but it's not -- no teletype-like device EVER used Baudot's code,
it was for manual (finger) input) 5-bit code with two code tables
(aka cases) selected with FIGS and LTRS. They mostly run at 60
wpm, aka 45.45 baud.
Besides the speed issue, which requires good buffering or
per-character flow-control handshaking (not commonly done well,
and not possible on msoft OSs past DOS), you need a little state
machine for code table/case translation each direction, and then
about 1/2 the ASCII code set simply doesn't exist in ITA2, and
there are no control codes in common except CR, LF, bell and NUL.
Plus unless you re-wire them they are all half-duplex; pressing
a key prints locally. ASR33's are 20mA current loop, but the
older devices want 60mA, and 100 volts on the loop with a big
series resistor; the current risetime requirements make it so.
3:42 p.m.
Tom Jennings wrote:
On Sat, 11 Dec 2004, Fred Cisin wrote:
ASR-33's and their ilk are ASCII and 110 baud (43's do 300
I think).
The TTY-for-the-deaf tech is based upon older ITA2 (aka "baudot"
but it's not -- no teletype-like device EVER used Baudot's code,
it was for manual (finger) input) 5-bit code with two code tables
(aka cases) selected with FIGS and LTRS. They mostly run at 60
wpm, aka 45.45 baud.
Teletype Corp. Models 14, 15, 19 and 26 for a few plus some by other
companies used Baudot code. Some of those were interfaced to early
micros for lack of a better/cheap console at the time.
Besides the speed issue, which requires good buffering
or
per-character flow-control handshaking (not commonly done well,
and not possible on msoft OSs past DOS), you need a little state
machine for code table/case translation each direction, and then
about 1/2 the ASCII code set simply doesn't exist in ITA2, and
there are no control codes in common except CR, LF, bell and NUL.
Plus unless you re-wire them they are all half-duplex; pressing
a key prints locally. ASR33's are 20mA current loop, but the
older devices want 60mA, and 100 volts on the loop with a big
series resistor; the current risetime requirements make it so.
7:38 p.m.
On Sat, 11 Dec 2004, John C. Ellingboe wrote:
Teletype Corp. Models 14, 15, 19 and 26 for a few plus
some by other
companies used Baudot code. Some of those were interfaced to early
micros for lack of a better/cheap console at the time.
It's often called "baudot", even the ARRL handbook calls it that,
but it's actually ITA-2. Baudot has accented characters and
"No." and a few oddballs, no format effectors (eg. CR, LF, etc).
I never could figure out how "baudot" became the vernacular
for ita2 tty code.
http://wps.com/projects/codes/index.html
12 Dec
12 Dec
9:13 a.m.
Tom Jennings wrote:
The TTY-for-the-deaf tech is based upon older ITA2
(aka "baudot"
but it's not -- no teletype-like device EVER used Baudot's code,
John C. Ellingboe wrote:
Teletype Corp. Models 14, 15, 19 and 26 for a few plus
some by other
companies used Baudot code. Some of those were interfaced to early
micros for lack of a better/cheap console at the time.
AFAIK, the model 28 and 32 use the same five-level code as the 15 and
19. The model 32 is the five-level version of the better-known model 33.
Tom's point is that contrary to popular belief, the five-level
Teletype code is NOT actually the Baudot code. His web page on the
history of character codes explains this in great detail with
references:
http://www.wps.com/projects/codes/index.html
Years ago my friend Jim Philips interfaced a model 28RO to his
semi-homebrew 6502-based TLB computer. He wired up some sort of circuit
to turn off the motor when the line when idle (spacing) for more than
a minute or so. I wrote a driver for the APEX operating system, which
normally used ASCII. The driver performed the necessary code conversion.
The tricky part was what to do about printing characters that had no
five-level equivalent. I decided to use overstrikes (somewhat like APL
in principle). The driver kept track of whether any characters on the
current print line needed overstrikes, and if so, would print one pass,
carriage return, second pass, then another CR and a line feed.
I think that's the oldest piece of code I've written for which I still
have source. I doubt that it's of use to anyone, but there are two
versions of it on my web site:
http://www.brouhaha.com/~eric/software/ttyhan/
I'm still hoping to recover my program from the same era to format
eight-inch disks on a 1771-based controller.
Eric
7157
days inactive
7158
days old
5 comments
5 participants
participants (5)
-
cisin＠xenosoft.com -
eric＠brouhaha.com -
john＠guntersville.net -
msokolov＠ivan.Harhan.ORG -
tomj＠wps.com