14 Aug
2010
14 Aug
'10
11:20 p.m.
Dave McGuire <mcguire at neurotica.com> wrote:
Apparently so. :-)
Yup. I just learned. All I've ever seen have been with detachable cords.
But as I wrote above, I bet this is a european thing.
All mine do, and I have four right here.
Huh? That is totally backwards in more than one way.
Yes, MMJ "fixed" one thing. It has nothing to do with ethernet, but all
to do with people (and companies) who couldn't figure out how to wire a
DB25. Almost all companies got the gender wrong on their equipment. In
addition to that, many couldn't figure out what a DTE and DCE was.
Now, that is called standard violation. Causing people to have cables
they think they can connect, but which don't work. DEC is one of the two
companies that did get it right (the other one being HP). To this day,
it totally amaze me how so many companies couldn't get this right. And
I don't know. When was the end of the monochrome CRT era? Has it ended yet?
Dave McGuire <mcguire at neurotica.com> wrote:
Ouch. You're right. For some reason I was thinking that the VT220 also
had MMJ, but it didn't. That only came with the VT320...
But I can't see the relevance of MMJ vs. RJ45 either, for various
reasons mentioned above.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
On 8/13/10 4:27 AM, Johnny Billquist wrote:
Hmm. Unfortunately I don't have any VT320 around anymore, since all of
them have broken down (flybacks mostly). But I've had atleast five of
them over time, and all have had removable cords.
I wonder if this might be more of a european thing. Since different
countries in Europe use different power plugs, it makes sense to have
the power cord detachable. There is more or less a standard format plug
that goes into any kind of computer equipment, but the wall plug differs
between countries. So you usually don't use a fixed power cord, but
instead the standard equipment power connector on your equipment, and
then ship whatever power cord is used in that country.
> >> Not at all, I just wanted to know
what he didn't like about them. The
> >> only thing I dislike about VT420s is the non-removable power cables.
>
> Huh? My VT420s have removable power cords...
Mine do not. This is interesting. I know there was a variation of
the VT320 (yes 320) that had a removable power cord, but they're not
terribly common. Apparently there's a removable-cord version of the
VT420 as well. Interesting! > The VT420
have both DB25 and MMJ, so I can't see how that could annoy
> anyone. (As do all DEC terminals from the VT220 onwards.)
Now waitaminute. I am staring at the back of both a VT420 and VT320
right now, on the table opposite my desk. Neither of them have DB25s,
only MMJs. The VT420 has what looks like a knock-out that's about the
right size for a DB25.
Apparently versions with and without DB25s exist as well! That same (rare-to-me) VT320 I mentioned above that
has a removable
power cord also has a DB25. Out of a few hundred VT320s that have gone
through my hands, it's the only one I've ever seen that has either a
removable power cord or a DB25. I've never seen a VT420 with either of
those, and until now, I haven't even heard of their existence.
Well, I have four VT420 at home right now, and they all have both a DB25
and detachable power cord. Since I was feeling creative tonight, I even
took pictures of the back side of all terminals I have at home.
So here is a link to where you can see the backside of:
VT-330, VT-420, VT-510, VT-520 and VT-525. All of them have DB25 and all
of them have detachable power cords.
http://www.update.uu.se/~bqt/vt
(Argh, I just realized I missed the VT-240 I have, but oh well...)
William Donzelli <wdonzelli at gmail.com> wrote:
> Huh? My
VT420s have removable power cords...
Some do, some do not. > The VT420
have both DB25 and MMJ,
Some do, some do not. Of the fifty or so I had recently, I think only
one had the DB25 in addition to MMJ. > However,
MMJ is actually very nice. Too bad it didn't catch on outside of
> DEC. But I try to use it for everything I can at home.
MMJ "fixed" a problem that really was no big deal - people confusing
RJ45 serial with ethernet. I think the real reason was to lock people
into MMJ by doing the old lets-violate-the-standard trick. In my book,
DEC is guilty as anyone else here. from that perspective it don't surprise me when
people around here don't
get it either (there was a long thread not long ago,
which I declined to
even participate in). RS-232 is so simple that it's hard to get wrong.
There is only two things you can mess up with. Connector gender, and DTE
vs DCE. How can people find that so difficult???
And if people and companies had actually stayed with the standard, you
wouldn't even had been able to mix those to parameters up.
A DTE *should* have a *male* DB25. A DCE *should* have a female DB25. A
male-male cable should be crossed, a female-female cable should be
crossed, a male-female cable should be straight. There is nothing more
to it.
All terminals and computers are DTEs. Modems are DCEs. But it you
absolutely wanted to, feel free to wire a modem up as a DTE. It will
work just fine, just as long as you fit the right DB25 to it, and wire
it up accordingly.
But no. Companies just loved putting female DB25 on their terminals, and
wire them up as DTEs. Or put male DB25 on their computers, and wire them
up as DCEs. *Idiots*
That is called violating the standards.
And to make matters ridiculously worse, we have IBM. Who simply put just
raped the RS-232 standard by using a DE9, moving one or two pins in a
totally non-logical way, changing the gender, *and* sortof wiring it as
a DCE.
They should be taken out to the back and shot. IBM have caused more
damage to the computer world than all other companies put together.
Here is a simple tip for the next time you wire a RS-232 up. Measure pin
2 and 3 on the equipment. One should at around -12V, while the other is
around 0. Do this on both sides. Then wire the -12V from one side to the
0V on the other for both 2 and 3. And run pin 7 straight through.
And that's it. You now have a correct RS-232 cable, albeit just the data
leads. You can wire the rest up if it amuse you. The most important ones
are DCD, DTR, DSR, RTS, CTS. For a DTE-DTE, you should wire CTS to RTS
and DCD+DSR to DTR. Very simple. And if I remember right, we're talking
about pines 4,5,6,8 and 20. But I'd usually check the RS-232 DB25
connector layout before I try to wire a full cable up. Most of the time
I'm happy with just 2,3 and 7 anyway, since I don't do hardware flow
control (another RS-232 standards violation, by the way, and which DEC
did not do). But having the DSR signal is useful to detect if someone
gets disconnected.
What DEC did with MMJ was in no way violating any standard. Noone in his
right mind would think that an MMJ was an RS-232. So what standard did
they violate (if I may ask?). Hmm, I seem to remember that the
signalling in the MMJ is even called DEC-423, but I might be remembering
wrong. It is pretty much compatible with RS-423 anyway (might be
equivalent), and you can usually get away with connecting that directly
with RS-232, but they are not really the same thing. (Hmm, looking at
RS-423, it would appear that DEC-423 is a superset, since DEC-423 don't
actually use a common ground for everything, but use one ground for all
transmitted signals, and one ground for all received signals).
So, the signalling in the MMJ connector is only claimed to be
communicating using DEC-423. How would that violate any standard? If DEC
had said that it was an RS-232 port, then they would have violated the
RS-232 standard. (I guess I'm confused at your definition of violating a
standard.)
What MMJ solved was that they removed the gender issues, and they
simplified the DTE/DCE issues. Your cable is either straight or crossed
(either flat or turned 180? looking from one end to the other). They
also simplified the assembly of the cables compared to RS-232. The fact
that MMJ
Ethernet vs. RS-232 on a RJ45? Give me a break. None of that even
existed when the MMJ came about. And the idea of putting RS-252 on an
RJ45 is something I'd call violating a standard, if anything. But it
comes with the one-connector-for-everything that some people are so fond
of. So you also have telephony on RJ45, to make life really
interesting... And all running through one patch panel.
> The
reliability of the VT420 seems to be pretty decent. I've had many more
> VT320 fail on me. But we have to remember that we're talking about 20+ year
> old equipment now...
Yes, but these were built well towards the end of the monochrome CRT era. On 8/13/10 5:51 PM, Johnny Billquist wrote:
I said "unless you count the used defined font". :-)
All that said, I know some crazy person wrote a GIF viewer for the
VT320, using the user defined font to pull it off.
Dave McGuire <mcguire at neurotica.com> wrote:
On 8/13/10 8:49 PM, William Donzelli wrote:
> >> AFAIK the VT420 supports Sixel,
but not ReGIS.
>
> No. The last graphic terminal was the VT340.
> The VT420 don't support any graphics, unless you count the user defined
> font as graphics.
>
> Graphics implies either SIXEL, ReGIS or both. Actually, I've never seen
> any terminal that supports sixel but not ReGIS, however, several
> printers is of that inclination.
>
> (Although I'm sure someone will now recall some terminal that do sixel
> but not ReGIS just because I wrote the above... :-) ).
I've never *used* Sixel graphics on a VT420, but the manual clearly
states that it supports the Sixel format.
(flip flip)
Ok, I just went back and re-read it. It "supports Sixel format" as a
way to encode user-definable character sets. So you're right I suppose,
it ALMOST supports Sixel graphics! ;) > >>
However, MMJ is actually very nice. Too bad it didn't catch on outside of
> >> DEC. But I try to use it for everything I can at home.
>
> MMJ "fixed" a problem that really was no big deal - people confusing
> RJ45 serial with ethernet.
Huh? I don't see how that can be. The 802.3i standard which defined
10baseT Ethernet on RJ45 connectors came out in 1990, while the first
terminal to implement MMJ was the VT320, which predates that by three years.