<div dir="ltr">OK.... I just learned something...<div><br></div><div>The "D" type connectors were introduced by Cannon in 1952.</div><div>The second letter is the size.</div><div>DA-15</div><div>DB-25</div><div>DC-37</div><div>DD-50 (this was the one used for SCSI for a while)</div><div>and DE-9</div><div><br></div><div>Wow!</div><div><br></div></div><div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br>
<a href="#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2" width="1" height="1"></a></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Mar 8, 2019 at 7:41 PM Texx <<a href="mailto:texxgadget@gmail.com">texxgadget@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Improvements in cable enabled pushing the RS232 standard.<div>When you look at those twisted wire pairs, you are looking at the magic.</div><div>The specs of the cable depend on the number of twists per foot and the insurance that the spacing between </div><div>the surfaces of the wires inside the insulation remaining fairly constant.</div><div>This is the difference between the various "CAT" numbers.</div><div><br></div><div>The original EIA RS-232 spec was written for Cat-2 cable which was not much more than twisted doorbell wire.</div><div>Data speeds improved somewhere between CAT-2 & CAT-3.</div><div>The first ARPANET links I believe were 19k before later upgrading to 56k.</div><div><br></div><div>The telco industry adopted an Amphenol connector for 25 pair cables.</div><div>Later, Centronics adopted a shorter version of the same connector (36 pin/18 pair)</div><div>I still run into morons who call them all Centronics (25 pair, 28 pair, even DB-25)</div><div>This was sad when a telco employee told me that the phone co adopted the connector after Centronics did.</div><div><br></div><div>Further complicating things, SCSI has been done on a 25 pair amphenol and a DB-25.</div><div>When I used a DB25 cable to connect serial ports, I got yelled at "You cant use that cable! Thats a PARALLEL cable!"</div><div>Oh yeah, after the demise of the centronics printer port they used a DB25 for THAT too!</div><div><br></div><div>People who think they know everything annoy the hell out of those of us who DO!</div><div><br></div><div><br></div></div><div id="gmail-m_2840582429504304258DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br>
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</tbody></table><a href="#m_2840582429504304258_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2" width="1" height="1"></a></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Mar 4, 2019 at 8:58 PM Michael Paoli <<a href="mailto:Michael.Paoli@cal.berkeley.edu" target="_blank">Michael.Paoli@cal.berkeley.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">> From: "Rick Moen" <<a href="mailto:rick@linuxmafia.com" target="_blank">rick@linuxmafia.com</a>><br>
> Subject: Re: [conspire] DE-9, not DB-9 (was: conspire list hacked?)<br>
> Date: Mon, 4 Mar 2019 16:33:22 -0800<br>
<br>
> have locked the serial port to 115,200 bps rather than 38,400. (I don't<br>
> know if any RS-232C ports supported 224,000 BPS, and no longer care.)<br>
<br>
Another bit of trivia for RS-232-C spec.<br>
Max speed one could do without bending(/breaking) spec. was "38.4"(k),<br>
or more specifically 38,400 - at least of the standard<br>
speed doublings up from 300. And why? Had to do with the maximum<br>
rise/fall times on the voltages plus the minimum thresholds of level<br>
(and hold time probably also) for the voltages, to have a legitimate<br>
to-specification signal.<br>
<br>
"Of course" the specification got, uh, bent a lot, and higher speeds<br>
were pretty common (at least on the wire) in fairly quick* order.<br>
Much of the earlier stuff only had top wire speed of 9600, if I recall<br>
correctly - and I think that was due to spec limitations on the common<br>
(TTL to RS-232-C) level conversion ICs that were most commonly used<br>
at that time. Or maybe(?) it was 2 or 4 x that, but no higher, until<br>
subsequent faster speed capable chip sets came along.<br>
There are also successor standards that support higher speeds, and<br>
are mostly (at least signal-wise) backwards compatible with<br>
RS-232-C.<br>
<br>
*quick ... well, if one thinks from about 1969 to about 1985 as quick order.<br>
<br>
Oh, other bit I forgot ... Electronics Industry Association (EIA) - wrote<br>
and copyrighted the RS-232-C specification. That's also why at least some<br>
of the equipment also had "EIA" marked by their RS-232-C ports - to help<br>
identify what they were.<br>
<br>
And just because it's a DB-25 doesn't mean it's RS-232-C. Could be<br>
"Centronics compatible" (signal levels) printer port, or SCSI! So,<br>
generally best to never presume. Some would also do funky things on<br>
DB-25 connectors. E.g. I recall I had a UPS ... as for RS-232-C on that<br>
port (and yes, as well documented in the manual) ... yes, for the<br>
customary signal ground, data transmit and receive lines (on primary channel).<br>
But others used for very different things - e.g. EPO signal to UPS (N.O.,<br>
close contacts, UPS shuts down cold immediately). I think it had some other<br>
non-RS-232-C signaling on there (UPS alarm and/or on UPS power).<br>
So, case like that, one wouldn't want to just connect a full 25-line straight<br>
through cable from UPS to terminal - in fact the manual very specifically<br>
spelled out to NOT do that.<br>
<br>
<br>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail-m_2840582429504304258gmail_signature"><br>R "Texx" Woodworth<br>Sysadmin, E-Postmaster, IT Molewhacker<br>"Face down, 9 edge 1st, roadkill on the information superdata highway..."<br></div>
</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><br>R "Texx" Woodworth<br>Sysadmin, E-Postmaster, IT Molewhacker<br>"Face down, 9 edge 1st, roadkill on the information superdata highway..."<br></div>