---------------------------------------------------------------------- Message-ID: <ef7a673e-4465-41d6-872f-254d54876d66@googlegroups.com> Date: 30 Nov 2019 11:26:01 -0800 From: HAncock4 <withheld@invalid.telecom-digest.org> Subject: Re: History Western Union Telex ads On Friday, November 29, 2019 at 1:41:17 PM UTC-5, Bill Horne wrote: > On Wed, Nov 27, 2019 at 01:27:01PM -0800, HAncock4 wrote: > > On Wednesday, November 27, 2019 at 10:34:36 AM UTC-5, Bill Horne wrote: > > > Ultimate trivia: how many separate symbol combinations are used in the > > > version of Murray code employed for Telex, and why? > > > > According to the WU Technical Review, there were different variants of > > the Baudot code used in different applications. For example, certain > > uses had fractional symbols. Another use had weather symbols. It > > didn't really matter as long as the keyboard and typebars of the > > sending and receiving machines were coordinated. > > Sorry, I didn't write my question clearly. I wasn't asking about > changing keytops and type pallets, which would IIRC be at the > "Presentatin" layer of the OSI Reference model: I don't doubt that it > was commonplace, but (again, IIRC) I was asking about the "MAC" layer. > > There are 32 combinations of bits available from a 5-unit code such as > Baudot/Murray. They weren't all used, though, at least in the CCITT #2 > alphabet, and I'd like to know why. I'm not sure if this article from the WUTR answers your questions, but it is an interesting look at the code variations and teleprinters used by Western Union in the 1950s: http://massis.lcs.mit.edu/telecom-archives/archives/technical/western-union-tech-review/10-1/p037.htm ------------------------------ Message-ID: <CANog7L5gTuezFYmri=GYCtm_BWPytYqbRY8qC=WNhdkt-E87yQ@mail.gmail.com> Date: 1 Dec 2019 15:44:49 -0500 From: "Charles Jackson" <clj@jacksons.net> Subject: More #2 Julian Thomas asked: > Would it be that the code point with no holes wasn't used? The code point with no holes represents the blank character. The code point with all holes is Letters-shift. IIRC, Baudot, like ASCII, used mark-hold. So an idle line was carried a continuous mark signal. Characters were represented by 7 elements, (spacing element, five code-point elements, mark element). The mark-to-space transition signalled the beginning of a new code symbol. Chuck ------------------------------ Message-ID: <CANog7L5oUkeDQnNJFXHB0EcfMtY=SbODjJLk4xpSnBcDRJ7FoA@mail.gmail.com> Date: 1 Dec 2019 15:36:30 -0500 From: "Charles Jackson" <clj@jacksons.net> Subject: Why unused CCITT #2 codes Bill asked: There are 32 combinations of bits available from a 5-unit code such as > Baudot/Murray. They weren't all used, though, at least in the CCITT #2 > alphabet, and I'd like to know why. > > Bill The book Principles of Telegraphy (Teletypewriter) at https://books.google.com/books?id=PfAwJXixemAC&printsec=frontcover#v=onepage&q&f=false states that three codes in CCITT Alphabet #2 are unassigned. Figures case (shifted) F, G, and H are described as "Unassigned internationally, may be used with local meanings in national systems." Figure C-2 shows them as !, & and STOP in the "U.S. Military Communication Alphabet." Chuck ------------------------------ Message-ID: <7df7e380-9d87-4a0a-bb80-f0559ec92ad6@googlegroups.com> Date: 30 Nov 2019 12:15:10 -0800 From: HAncock4 <withheld@invalid.telecom-digest.org> Subject: History GTE ad 1972 interconnect Historically, General Telephone/Automatic Electric sold their equipment to (1) independent telephone companies and (2) to businesses seeking a private internal system that was not connected to the outside Bell network. But in 1972 GTE/AE was advertising their systems to business in direct competition to Bell, as shown by the following ad in a business magazine: https://archive.org/details/Nations-Business-1972-06/page/n45 (two pages) Also, in that issue Bell advertised its 800A PBX https://archive.org/details/Nations-Business-1972-06/page/n67 ------------------------------ ********************************************* End of telecom Digest Mon, 02 Dec 2019