Dr. James Marsters, TTY deaf service developer [telecom]

On Sun, 06 Sep 2009 21:02:31 -0400, Robert Bonomi wrote: .........

......... Don't start mentioning "Null-modem" cables or I might start a rant on the

I still recall how badly some companies implemented RS-232 connections, Nortel were notorious for being clueless on this with the Meridian 1 systems.

The DCE/DTE problem was always fun. Back when we used 25 pin connectors for EIA232, I remembered "terminal talks on two" to keep it straight. I always thought all equipment should have the same pinout and cables should be reversing (null modem). Then you could connect anything to anything. That should also be done today with UTP Ethernet on RJ connectors. Make all cables reversing (like a typical telco line cord). Make all jacks the same.

Today, designing with microcontrollers, many have UARTs with RTS/CTS. But, which is the output, and which is the input? I always have to go looking deep in the datasheet and them noting it on the schematic to keep it straight.

Also, my first experience with RTS/CTS was with a Lear Siegler ADM-1 terminal. It could do a batch send (escape-4 to send a line, escape-5 to send the screen). It would make RTS go true and wait for CTS to go true before starting to send. Today, RTS/CTS seems to mostly be a bi- directional CTS. If it's true, the device receiving the RTS or CTS is allowed to transmit. If not, it has to wait.

On wire services, I recall the demodulator sitting under the model 15 was made by Lenkurt or something like that. I think they used different audio tones for different services with all services being on the line (at least it sounded like that when I listened to the line).

Harold

If all the cables are wired for "crossover" connections, then devices which transit an even number of patch bays wouldn't work. Making switches and hubs use DCE connections and everything else DTE keeps the rest of the wiring simple: it's _always" "straight across" unless it's a switch-to-switch connection.

That's right: the Lenkurt demodulators (I don't think they qualified as "modems", given their limited capability) could handle 16 channels IIRC. Running multiple services on one wire was a big cost-saver back then: each demodulator had filters for the channel that was fed to the Teletype.

Bill Horne (Filter QRM for direct replies)

I need to correct my earlier answer:

It was in 1979 or early 1980, right after I returned to Ma Bell from my first layoff. CBBS didn't go online until 1978, so it couldn't have been 1973 or 1974.

Bill Horne (Filter QRM for direct replies)

Hah! You date things from CBBS! Traditionally, we celebrate the anniversary of February 16, 1978, although it probably went live a week or two earlier.

Ward Christensen probably remembers me to this day: I kept pestering him to turn off the echo on the connections so that I wouldn't see every character I typed showing up twice. When I finally got my H-89 built and dialed into CBBS with a "real" computer running 300 Baud, he broke in and typed "Hey, Speedy!". ;-)

Ward (and Randy Suess) had a long history of randomly breaking into CBBS sessions with comments (and not nice ones if it was Randy and you were doing something he didn't like). They were/are interesting guys. * --

• PV Something like badgers, something like lizards, and something like corkscrews.

It's a shame that the World Wide Wait pushed bulletin boards aside: IMNSHO, it was better to have small machines that dealt with a local audience and had someone to mind them.

The Internet, or at least the Web, has turned into an advertising vehicle, and if you're not buying, the commercial site owners aren't interested in helping you. Yes, there are exceptions, but they're not the rule.

Bill Horne

And you had computers that didn't set some of the lines right, so you might use carefully-spliced cables (or a gadget from radio shack with jumpers and opposite-gender connectors on both ends) to duplicate signals. And null modem adapters. And gender changers. And then they added 9 pin serial...

I used to have a kit of cables and dongles to cover every possibility so I could later go back and make a proper cable, and it was NOT a small kit. *

Would anyone know what platform this BBS used?

Sounds like you should've been transmitting in full duplex. Most modems and terminals had a switch somewhere to set the duplex, though sometimes the switch was tiny and hard to find.

Regarding the possibility of your Teletype machine being multi-use (able to do TWX tones and dial-up tones), it was not uncommon in the Bell System for the "under the hood" components to be upgraded even if the unit remained the same on the outside. The last models of the 500 set were very different than the first models for that reason*, though they looked nearly the same.

I'm speculating here, but given the time frame--late 1970s--perhaps the TTY in the toll office was upgraded so that it could do double- duty, indeed, given the growing data traffic of that time, it's likely it would be a very useful function. (Of course, maybe the TWX/dial-up tones were the same all along.)

• In their 25 year lifespan, the dial, network, ringer, transmitter, and receiver were all redesigned and improved.

Given that it was a company machine and was in daily use for other things, I didn't feel it would be a good idea to alter its settings: there was no switch (I looked), so I had to eenndduurree.

I really doubt that components used in the machine were upgraded: it was a TWX machine in all but name, and it even had a card dialer. I used it to test TWX lines on a couple of occasions - it never occurred to the WU techs that anyone could do that, so it was a very good tool for proving troubles back to them when they claimed a fault was in our network.

In addition to Ward Christensen's CBBS, I also used it to connect to the Heath User Group BBS in Massachusetts. The modem worked on both BBS and TWX connections, without any noticeable change in tone during the setup handshake.

Long story short, I don't think there was ever a different tone set for machines used on TWX vs. those used on the PSTN. If there ever was a different tone set, I'd like to hear from those who can clear up the mystery.

Bill Horne

I fired up my Apple II with my GBBS, I'll be off until next year so I'll have time to work on it and getting it online again.

I once let the magic smoke out of a $1000 printer because it never occurred to me that a product designer would have wired a power source into a RS232 connector. The printer wasn't working, then I noticed a wisp of smoke literally coming out of it. I think the offending instrument was a Morrow MD-2 computer, which had two female DB25 outputs connectors, one DCE and the other DTE (a terminal connected to one, and your choice of modem, printer, or A-B switch connected to the other).

Gosh, I haven't used my "christmas tree" or little jumper box in years. I don't miss it at all.

Dave

When were you on CBBS?

Ward and Randy invented the BBS. Bill is recalling about a significant moment in computer history. This invention predated Usenet and the Web.

Here's Randy's narrative. This article is undoubtably in the Telecom Digest archives.

The original CBBS consisted of a S-100 motherboard picked up at some fleamarket. This was a "kit" of course, so I had to solder all the connectors. (lotsa soldering done in those days, such as 8 k memory boards filled with 1kX1 chips)

It was mounted on a BUD chassis with a single density 8 inch floppy drive. On the motherboard was some 8080 cpu (upgraded to a Z80) a Hayes 300 baud modem card, a 3P+S board with the parallel port used for control signals, a Processor Technology VDM video display card, and an 8k memory board. There was also a card with 8 1702 EEPROMS that held the CP/M BIOS, video display drivers, and debug code, all written by Ward. I had a EPROM burner, and Ward made sure all the BIOS variables and experimentor stuff ended up in the last 1702. Musta re-programmed that sucker 10 times a week for a few months.

The floppy drives of that time had 117vAC running the spindle motor, and the drive would wear out quickly. So I built a circuit on a prototype board that would turn on the system power when a ring signal came in from the modem card and do a reset of the computer. By the time the drive spun up, the software had answered the phone and booted CPM and CBBS from the floppy. (simple power fail system!) The circuit board also had some 555 timers, so when the caller went away, the drive motors would continue to spin for about 10 seconds to flush out any data, then shut the system down. I had an old Heath chart recorder I hooked across the floppy drive motor and set up the chart speed for 2 days per sheet. Was able to determine the calling patterns from the chart.

From the 173k single density single sided floppy, we went to a pair of them, then to double density double sided drives. Bout a year later, moved CBBS to a NorthStar Horizon cabinet with a 10 meg seagate hd. Both those systems are still sitting around someplace. It is now running on a PC clone motherbard still running CP/M with the original 8080 assembly code! The clone board has a V20 chip, which fully supports the 8080 op codes. Ward wrote a wrapper around CP/M-CBBS, and CBBS has been running that way for over 15 years.

DTE is male. Ma Bell is female. It's what the original standard says. Of course, nobody paid attention to the standard, which is how we got into this mess.

This has not changed.

This is inexcusable and is the result of poor programming on the result of microcomputer vendors. You did not see this in the big computer world. Back at that time there was a huge influx of hobbyists coming into the microcomputer world who didn't really know what they were doing, did not know that standards already existed, and they found themselves making commercial products. It was a very weird time.

This also has not changed.

--scott

-- "C'est un Nagra. C'est suisse, et tres, tres precis."

ISTR a news story about Philippe Kahn, founder of Borland, who, while observing a Microsoft demonstration that involved dialing in to some online service they were pushing, stood up and asked why the modem lights weren't blinking.

Bill Horne

Yes, but with qualifications.

Yes, you generally did not see this in the business mainframe world because work had to get done - employees and vendors waiting for their checks would have no tolerance for an excuse, "well, the pin connectors weren't as we expected". Work had to get done on time per schedule*. Indeed, big shops had reciprocal backup arrangements with another shop, so if their machine was down, they could run their critical reports at another site.

Sometimes big shops would tinker with 3rd party add-on peripherals which sometimes worked well, sometimes not. But these normally would be on less critical applications and a backup on hand.

In the science/academia world there was more experimentation with peripherals, especially if a lab had its own mini computer to experiment with.

The flip side is that in the nascent micro-computer world, which was much more hobbyist than business in its early days, the era of experimentation produced many technical advances. It enabled end- users to really get into the guts of the new technology, certainly not possible or allowed with a mainframe. Mainframe technology moved forward slowly, indeed, IBM purposely set up its new PC division to be separate for that reason.

My objection to that early experimental micro-world was that individuals and entrapreneurs passionately claimed a hardware or software [item] was fully developed and ready for the rigors of demanding real-world business service, when in fact it was most certainly not. Many end-users fell in love with a sales pitch of a micro, but closer examination often found the hardware was severely underpowered for its anticipated needs and the software's functionality was not as robust as claimed.

In those days many mainframers found themselves in the unpleasant situation of rushing to bail out a critical end-user who bought a micro-application which didn't work.

• I knew a junior programmer whose program crashed in the middle of the night. They called his house but his father refused the call. The programmer was fired the next day.

"Underpowered" doesn't begin to cover the rapacious and sleezy conduct of some micro vendors. I heard of one retailer which sold machines equipped with 64K of RAM, but never recompiled CP/M to recognize the memory beyond it's default 56K setting. When customers asked for a memory upgrade, the vendor would do the recompile and then charge them as if they had actually installed the added RAM.

It was a gold rush, and the winners were the ones who kept their eye on the gold.

Bill Horne

I signed on every couple days from high school practically from the day they opened the modems. *

It was a purpose-built S100 bus computer, and custom software. *

And -printers- that used non-standard pins for various handshaking.

At this remove, I don't remember which one, but one of the _big_ letter-quality printer manufacturers (NEC, Diablo, ??) was *notorious* for this.

That reminded me of the time I plugged a modem - I can't for the life of me recall the name, though I recall that it was selling like mad at the time because it was really cheap - into an Amiga. As it happens, the Amiga used a couple of 'reserved' pins for power (+ and - 12V, according to a pinout I found via Google), and the modem manufacturer used them for something entirely incompatible. I do not recall whether the Amiga was damaged or the modem was converted into the doorstop it so strongly resembled.

What I hated was crimping all the pins for custom connectors.

All these posts about poor equipment manufacturing do seem to demonstrate why the old Bell System--and regulators--were so hesitant to allow customer owned equipment to be connected to the network. What good were 'standards' if they weren't followed?

"Standards" has many meanings: if used to exclude competitors from any meaningful opportunity, then standards are conterproductive. If used to assure a level playing field, vice versa.

Bill Horne