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Message Digest Volume 28 : Issue 45 : "text" Format Messages in this Issue: Re: TTY 33 and 35 case and cover composition? Re: TTY 33 and 35 case and cover composition? Re: TTY 33 and 35 case and cover composition? Re: TTY 33 and 35 case and cover composition? Re: TTY 33 and 35 case and cover composition? Re: Teen sends 14,528 text messages in one month ====== 27 years of TELECOM Digest -- Founded August 21, 1981 ====== Telecom and VOIP (Voice over Internet Protocol) Digest for the Internet. All contents here are copyrighted by Patrick Townson and the individual writers/correspondents. Articles may be used in other journals or newsgroups, provided the writer's name and the Digest are included in the fair use quote. By using -any name or email address- included herein for -any- reason other than responding to an article herein, you agree to pay a hundred dollars to the recipients of the email. =========================== Addresses herein are not to be added to any mailing list, nor to be sold or given away without explicit written consent. Chain letters, viruses, porn, spam, and miscellaneous junk are definitely unwelcome. We must fight spam for the same reason we fight crime: not because we are naive enough to believe that we will ever stamp it out, but because we do not want the kind of world that results when no one stands against crime. Geoffrey Welsh =========================== See the bottom of this issue for subscription and archive details and the name of our lawyer, and other stuff of interest. ---------------------------------------------------------------------- Date: Thu, 12 Feb 2009 15:49:30 -0800 (PST) From: hancock4@bbs.cpcn.com To: redacted@invalid.telecom.csail.mit.edu Subject: Re: TTY 33 and 35 case and cover composition? Message-ID: <492aa038-781b-4b6a-9516-d16f6dee4698@v38g2000yqb.googlegroups.com> On Feb 12, 8:23 am, hanco...@bbs.cpcn.com wrote: > Clearly the 33 was designed for computer use as well as telegraphy and > I suggest the designers did an excellent job  especially given the > very limited computer time sharing capability when they began their > task.   I forgot to mention something very interestin the WU Tech Review ASCII article (see above for link). WU said it did not think ASCII would have much of a place in the WU network since it wasted three bits. Although at that time WU was very interested in serving as a data transmission carrier, choosing to avoid ASCII, in my humble opinion, condemned them to second rate status. If you get a telegram from me "SENDING YOU 500 DOLARS", you'll deduce I meant "DOLLARS", even if the transmission line dropped an 'L'. But computers don't have that luxury, they need the protection of parity detection (one of the ASCII bits). Further, computers require more printing characters and special control characters which Baudot had no room for. Computers did not store data in Baudot. Converting telegraph transmissions to computer code required complicated mechanisms to insert or detect the FIGS and LTRS command codes and act accordingly. Even if a computer is EBCDIC instead of ASCII, it needs to make only a one-to-one conversion. As we know, many computers were ASCII based. Thoughts? [Public replies, please] ------------------------------ Date: Fri, 13 Feb 2009 12:24:04 -0500 From: Bill Horne <bill@horneQRM.net> To: redacted@invalid.telecom.csail.mit.edu Subject: Re: TTY 33 and 35 case and cover composition? Message-ID: <RL6dneETXuQoMQjUnZ2dnUVZ_vOdnZ2d@speakeasy.net> hancock4@bbs.cpcn.com wrote: > On Feb 12, 8:23 am, hanco...@bbs.cpcn.com wrote: > >> Clearly the 33 was designed for computer use as well as telegraphy and >> I suggest the designers did an excellent job especially given the >> very limited computer time sharing capability when they began their >> task. The Model 32/33 was designed for TELEX and TWX service. When I attended the maintenance school in 1976, the instructors told us that Teletype provided a "private line" version of the machine only because some customers were still using private Teletype networks for sending orders to warehouses or to collect sales figures from dealers. They made it clear that these were light-duty machines, not to be used as printers or for keypunch. That was why they came with current-loop interfaces: it was the standard private line interface, and computer hookups needed either external RS-232-to-current-loop converters, or a modem that included a 20ma interface. > I forgot to mention something very interestin the WU Tech Review ASCII > article (see above for link). WU said it did not think ASCII would > have much of a place in the WU network since it wasted three bits. > Although at that time WU was very interested in serving as a data > transmission carrier, choosing to avoid ASCII, in my humble opinion, > condemned them to second rate status. I disagree: Western Union's fear of undermining their lucrative TELEX and TWX markets did them in, since competitors leapfrogged them by offering "bring your own modem" services which could carry any kind of traffic while WU tried to keep their existng TELEX/TWX customers in a closed system. > If you get a telegram from me "SENDING YOU 500 DOLARS", you'll deduce > I meant "DOLLARS", even if the transmission line dropped an 'L'. But > computers don't have that luxury, they need the protection of parity > detection (one of the ASCII bits). ASCII's parity bit proved ineffective for error checking on computer data lines: it could only detect single-bit errors, but the noise encountered on voice-grade data lines was as likely to "flip" multiple bits as it was to kill just one, so data transmission networks had to combine block transmission with cyclic-redundancy checks to assure reliable transit. A noise burst that flips bits 5 and 6 would change "500 DOLLARS" to "900 DOLLARS". The Model 33 machines I saw used as computer terminals were as likely as not to have the parity bit forced to continuous "marking": it caused premature wear on the bit 8 punch in the tape unit, but the computer programmers didn't want to hastle with parity errors and didn't think the effort was worth their time. > Further, computers require more printing characters and special > control characters which Baudot had no room for. Computers, per se, didn't require them: peripherals did. Most of the control characters in ASCII were intended for use with automated typesetting equipment and high-speed printers, which needed form control characters, such as form-feed, to work efficiently. > Computers did not store data in Baudot. Converting telegraph > transmissions to computer code required complicated mechanisms to > insert or detect the FIGS and LTRS command codes and act accordingly. > Even if a computer is EBCDIC instead of ASCII, it needs to make only a > one-to-one conversion. As we know, many computers were ASCII based. Converting _telegraph_ transmissions to computer code probably required an operator who knew how to use a Morse code key and sounder ;-). Kidding aside, I don't think the ASCII vs. Baudot conversion was that big an issue: 1. Baudot was used only on military and TELEX circuits, both of which were, by their nature, separate from the computer world. After PC's were established, Western Union did offer it's "Easylink" service, which could send and receive messages to and from the TELEX (and TWX) networks, but they controlled the conversion and customers didn't have to be concerned with it. 2. The Telnet and Tymenet services, both of which were X.25 based, offered transparent code conversion for almost all common coding systems. I had an Anderson-Jacobon 841 terminal, which used EBCD (not EBCDIC) coding, and Tymnet allowed me to connect it to timeshare systems and bulletin boards without trouble. 3. The computer revolution ramped up so quickly that most users never saw a Baudot machine, and the few who did have to deal with non-standard codes were usually geeks like me who could deal with the issue. My AJ-841 worked fine as a printer for my college papers, after I modified CP/M to do a lookup and convert from ASCII to EBCD, and changed the serial port initialization code to set the 8250 UART for six-bit words with odd parity. > Thoughts? I think it would be nice to have my Model 15 and my H-89 back again, but time marches on and I must use this laptop instead. Bill P.S. If AX.25 is no longer in fashion, I don't want to know. ;-) -- Bill Horne Temporary Moderator Telecom Digest (When sending a post to the digest, please put "" {without the quotes but _with_ the brackets} at the end of your subject line, or I may never see your mail. Thanks!) (Remove QRM from my address for direct replies.) ------------------------------ Date: Thu, 12 Feb 2009 23:12:45 -0500 From: Steve Stone <spfleck@citlink.net> To: redacted@invalid.telecom.csail.mit.edu Subject: Re: TTY 33 and 35 case and cover composition? Message-ID: <gn2rvv$13v$1@news.motzarella.org> > The amazing thing here we all are, 45 years later, using pretty > much the protocols developed way back then. Well... I don't think anyone uses current loop or answer back drums any more. I worked in a Western Union Teletype refurb shop in Mahwah, NJ in the late 70's. The division was called Western Union Data Services. We would squeeze all kinds of controllers, complete with meltdown drip pans, into the pedestals of the 33's towards the end to get them to match up with "modern" equipment. At the time model 33's were with a bank to bank funds transfer network called bankwire, and [they were also used by] the tobacco industry. I still saw a couple of TWX units go out the door every couple of weeks. Among other duties, I went to the Skokie, Il plant for model 40 printer training. I started in the disassembly room on the Model 33 side of the shop. About 95 percent of the 33's needed new plastic covers due to wear and tear or discoloration from heat or sunlight. As said in prior posts they were much lighter built than the older models. I got h*ll once from management for deviating from the official test tape verbiage. After two years I was bored to tears of brown foxes and lazy dogs. RYRYRYRY Steve 73 de N2UBP ***** Moderator's Note ***** Steve, Since you worked on 33's, then I bet you know why "RY" was not used. Semi-ultimate trivia question: what was the test sequence used in place of "RY" on Model 33's, and why? Ultimate trivia question: what was the key combination used on the Model 33 to punch a "leader" tape, having only feed holes without any other bits punched out? Bill Horne Temporary Moderator ------------------------------ Date: Fri, 13 Feb 2009 15:53:13 -0800 (PST) From: hancock4@bbs.cpcn.com To: redacted@invalid.telecom.csail.mit.edu Subject: Re: TTY 33 and 35 case and cover composition? Message-ID: <10bc59d7-615d-40c4-95af-c3a13949879f@l39g2000yqn.googlegroups.com> On Feb 13, 10:35 am, Steve Stone <spfl...@citlink.net> wrote: > Ultimate trivia question: what was the key combination used on the > Model 33 to punch a "leader" tape, having only feed holes without any > other bits punched out? It was cntl-shift something, cntl-shift P? Used to use it all the time. The tape punch had a arrow shape where the tape was torn off. I had a bunch of rolls of paper tape with BASIC programs punched on them, but I figured there'd be no easy way to print them, so there were trashed. ------------------------------ Date: Thu, 12 Feb 2009 15:49:47 -0800 (PST) From: hancock4@bbs.cpcn.com To: redacted@invalid.telecom.csail.mit.edu Subject: Re: TTY 33 and 35 case and cover composition? Message-ID: <6aa6d6c0-4daa-4a3f-9ffa-3d10e1d9d094@v39g2000yqm.googlegroups.com> On Feb 12, 8:30 am, "Dr. Barry L. Ornitz" <BLOrnit...@charter.net> wrote: > Baudot 5-bit machines.  All capital > letters were used, and to get more than the 32 possible characters, two > keys were dedicated to FIGS and LTRS.  To type a number for example, you > first pressed the FIGS key and then the key with the number on it.  Then > you pressed the LTRS key to go back to typing letters.  Often operators > would forget and garbage was printed leading to modifications like "unshift > on space."  At the end of a line, you pressed the return key, then usually > a few LTRS keys to allow for the physical time for the print mechanism to > return to the beginning of a line.  Then you pressed a key for a new line > (LINE FEED) unless you wanted to print over the line you just printed. > Again this was often forgotten.   Thanks for the information. Regular Teletype users quickly learned about LTRS/FIGS as well as return-line feed. Computer users often only typed return and the host computer returned the line-feed upon receipt of the data. Often computer users prepared a punched tape of their program in off- line mode, then transmitted it to save on connect time charges. We had to include a rub-out after return to give the carriage time to return to the side, otherwise the first character of a new line would not be at the margin. (Rub out was 8 bits punched, used to overwrite tape errors) > The old Baudot machines were asynchronous machines with a start and > stop bit; sometimes the stop bit was one and a half times the length > of the other bits.   ASCII TTYs was also asynchronous, with a start and stop bit. I believe the stop bit in ASCII was also 1.5 times the length. ***** Moderator's Note ***** Here's some more trivia: 1. What was the equivalent of the ASCII "Rubout" key on Baudot machines? 2. What was the relative length of the stop bit on Model 33 machines? Bill Horne Temporary Moderator ------------------------------ Date: Fri, 13 Feb 2009 11:49:33 -0800 (PST) From: furles@mail.croydon.ac.uk To: redacted@invalid.telecom.csail.mit.edu Subject: Re: Teen sends 14,528 text messages in one month Message-ID: <e3266adc-6183-4c3c-aa71-49aab61a5b6d@l39g2000yqn.googlegroups.com> On 17 Jan, 16:04, Stephen <stephenco...@gmail.com> wrote: > Wow! I can barely send 10 messages a day. The most is about 20 and > half of those are business related. I've sent five since the start of the year, and that's probably higher than average. ------------------------------ TELECOM Digest is an electronic journal devoted mostly to telecom- munications topics. It is circulated anywhere there is email, in addition to Usenet, where it appears as the moderated newsgroup 'comp.dcom.telecom'. TELECOM Digest is a not-for-profit, mostly non-commercial educational service offered to the Internet by Patrick Townson. All the contents of the Digest are compilation-copyrighted. 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