>Message: 26
>Date: Sat, 1 Feb 2025 18:13:17 -0500
>From: Nigel Johnson Ham <g4ajq1(a)gmail.com>
>Subject: [cctalk] Re: RS232 then and now
>
>On 2025-02-01 18:11, Chuck Guzis via cctalk wrote:
>> One mystery to me was why did the industry stick with the EIA-232 levels
>> for terminals and whatnot long after differential EIA-422 was
>> introduced. Higher-speed, better noise immunity, single-ended power
>> supply... Seems that the popular places were Appletalk and ST506 data
>> lines. But not on DTE/DCE. If you were using full-voltage (±15-±25)
>> at high speeds (>500Kbps), the slew rates were ridiculous.
>>
>> Inertia? My old 80286 motherboard had junper-selectable 232 or 422.
>>
>> Still have a couple of tubes of 422 drivers/receivers.
>>
>> --Chuck
>>
>DEC had RS422 available on their DLJ11J four-port interface, but I never
>saw it used in the field.
>
The Otrona Attache has two serial ports, DA-15 female, that are jumper selectable between RS-232C, RS-422 or RS-423.
Bob
In the early 70s my employer used stand alone data entry tape units in our remote locations. We started with NCR units but then switched to Tally. In the late afternoon the data would be transmitted to the home office in Chicago for processing. Also using NCR/Tally units. We used Racal-Milgo modems. These things were about the size of a large home stereo receiver. We started at 2400 baud. The units could do 3600 or 4800 (I don’t remember which) if a circuit board strap was moved.
We had locations in many cities/towns all the way out to Montana. It was decided that we needed to have the ability to switch between 2400 and the faster speed when possible. We did not want to have the locals power off the modem, open it up, remove a card and move the strap. So I got volunteered to come up with a plan.
I found a place in the modem where I could mount a switch. Luckily the modem had a sliding panel on the front so the locals would not have to open the box top. Went to our fleet garage where they had the tools I needed. I made a bunch of aluminum brackets for a tiny toggle switch. Added wires to the switch.
It was also decided that we could not trust the locals to do the switch install. So part of the plan included me going to all the locations and doing the install. I did not have a car at the time so I got a fleet car. Headed south to Kentucky then turned west. Don’t remember all the states I hit but I believe the last place I hit on the way home was Rockford. I remember being on a back road in Montana and I took a picture of my speedometer. I was doing 65. This was when there was a countrywide speed limit of 55. I can’t be limited by the Man. :)
Back at the home office we had 6 NCR/Tally machines and only 4 modems. I built a plug panel box that had everything wired to it and used telephone jack plugs to connect the Tally’s to an available modem. The box also had switches for the modem speed.
I now forget how long the whole process took. Put my DeVry AAS degree to good use. :)
Microsoft, or is it Micro-Soft or MICROSOFT, is a 50 yr. old trans-national
corporation. Whether it has been good or not-so-good for society is
debatable but on the financial-side its been very kind to investors(the
earliest ones anyways). Capitalism certainly owes Microsoft a good nod!
Happy computing.
Murray 🙂
Follow-up:
Vendor now on eBay for Fairchild 75325DC in lots-of-five; they accepted my
Best Offer.
https://www.ebay.com/itm/333675901157
So now I can get back to making some progress on repairing the H222A in my
MM11-DP :-}!
From: pbirkel(a)gmail.com
Sent: Friday, March 11, 2022 10:01 AM
To: General Discussion: On-Topic Posts <cctech(a)classiccmp.org>
Subject: Seeking a MC75325L Dual Memory Driver
I have here in my hands a DEC H222A (16Kx18), part of a MM11-DP, that took a
blow at sometime in the past. In consequence there are a number of small
parts damaged (snapped diode, crushed axial electrolytic, chipped mica
capacitor, cracked/broken SIP resister net) but those all appear to be
relatively easy to replace.
What's not so easy to replace is the MC75325L Dual Memory Driver (L =
Ceramic) that was de-lidded in the process :-<.
I am wondering whether anyone has one of these ICs in their spare parts
drawer that I could acquire?
I do see a MC75325P (plastic) on eBay at littlediode_components for ~20USD,
plus a surprisingly modest shipping charge (Royal Mail International).
UTSOURCE claims to have a supplier of the ceramic part "new", with a
significantly higher shipping charge.
Before I go with the ceramic part (IMO not the sort of packaging that gets .
remarked) I thought that I would check here for alternative sources.
Thank you,
paul
I prefer to use the Daily Digest mode. Then you can quickly glance at the topics and decide whether it is worth reading any particular messages. The pain comes when you may want to contribute something, as then you need to reconstruct enough of the message of concern in a new composition and reply that way.
Kevin Anderson
Dubuque, Iowa
Message: 3
Date: Thu, 23 Jan 2025 08:44:29 -0700
From: ben <bfranchuk(a)jetnet.ab.ca>
Subject: [cctalk] Re: AI? Really?
On 2025-01-23 8:15 a.m., Alexander Schreiber wrote:
On Tue, Jan 21, 2025 at 12:52:49PM -0700, ben via cctalk wrote:
On 2025-01-21 10:54 a.m., Paul Koning wrote:
Uh, what? How would the earth surface gravity be that much different? "Citation needed" as Wikipedia would say.
paul
https://en.wikipedia.org/wiki/Autodynamics
Ah, crackpot nonsense: "mainstream physicists have considered autodynamics
a crackpot theory for decades" - which is right there on the Wikipedia
page.
Kind regards,
Alex.
How lucky I am that I am not a "mainstream physicist".
A true scientist looks at the evidence, not what is discussed by others.
I also like the expanding earth theory, vs continental drift.
Where is all that energy to move the plates around.
The answer to your question is one that even mainstream physicists (Lord Kelvin) have gotten wrong in the past. See https://www.americanscientist.org/article/kelvin-perry-and-the-age-of-the-e…
A little humor for the group.
Among my other "legacy" systems I also have and still fool around
with a bunch of TRS-80's. Believe it or not, the Z80 based TRS-80's
were among the systems for which a version of STVOS was available.
Thought I would look to see if any of it was still floating around.
Asked Google
"TRS-80 Software Tools Virtual Operating System"
Got this result at the top of my response generated by whatever AI
engine they use.
--------------------------------------------------------------------------
A "TRS-80 Software Tools Virtual Operating System" refers to a software
program that allows a modern computer to emulate a vintage TRS-80
computer, essentially creating a virtual environment where you can run
old TRS-80 software, including operating systems like TRSDOS, by
simulating the hardware and functionality of the original machine,
letting you access and use programs designed for the TRS-80 on your
current computer.
---------------------------------------------------------------------------
That is the biggest pile of steaming poo I have ever seen come out of
any of the various AI engines I have run into. Not one piece of it is
accurate other than the mention of TRSDOS.
I also have a bunch of iRobot Roombas in my house. Based on my
experience with AI and robots I think there is no chance we will
have to worry about any Terminators in the future.
bill
