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#1
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generating morse code
On Apr 15, 6:11 am, (David Griffith) wrote:
When the key is down, the sounder clicks down. Let go and it clacks up. So, a dot is "click-clack" and a dash is "click-wait-clack". With most sounders, the sound of the armature going down is different from the sound going up, as you describe, so it's more than the time spacing. I think the Mark and Space stuff has to do with the fact that the line was always kept energized, thus, an idle line would hold the sounder arm down. That way you'd know immediately if there wa s a line fault. Yes, but there were several reasons for the normally-energized series line systems. 1) The first systems were powered by wet primary batteries called "gravity" cells. (You can still make your own - all you need is copper, zinc, copper sulphate, water and a jar). Unlike most other kinds of cells, the gravity cells need a load for best results. 2) The primary cells required a lot of maintenance and care. With a normally-energized system, line batteries were needed only at the ends of a line; the telegraph offices in between would not need them (except a cell or two for local loops). A typical line battery would consist of 100 to 200 gravity cells (often half the cells would be at each end) and permit operation over lines of 100 to 400 miles, depending on the wire size and number of intermediate stations. (#9 or #6 iron wire was commonly used for telegraph lines). So you can see the advantage of not needing line batteries everywhere! 3) Besides making a line break obvious, operation up to a break could be had by grounding the line at the last convenient point before the break. 4) Normally energized circuits made duplexing, multiplexing and other systems easier to implement. The wire telegraph was more sophisticated than some folks give it credit for being. ---- A telegraph story: There was a railroad which had an important position open at the division office. Applicants were told to show up on a certain day in the outer waiting room, and wait to be called into the Superintendent's private office for an interview. The outer waiting room was a busy place, with a telegraph sounder going continuously, various employees doing all sorts of tasks, and the Superintendent inside his private office with the door shut. A number of applicants showed up, most with years of experience. Each handed their papers to the clerk, took a seat, and waited. After all the chairs were occupied, a young man arrived - obviously not nearly so experienced as the others. He paused for a moment, papers in hand. Then he walked straight to the door of the Superintendent's private office, opened it, and walked right in, closing the door behind him! The other applicants looked at each other in surprise and some amusement. Barging in on the Division Superintendent was the best guarantee of never getting any job! One waiting applicant said the word "greenhorn" and the others all nodded. But a few moments later, the door of the Superintendent's office opened, and the Superintendent came out, followed by the young man. The Superintendent said: "Thank you all for coming, but the position has been filled." It was obvious that the young man had gotten the job they all wanted. Some of the applicants started to protest, but the Superintendent just pointed to the telegraph sounder. It wasn't on an outside line. It was playing the same message over and over: "If you can read this, come into my office" 73 de Jim, N2EY The |
#2
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generating morse code
N2EY wrote:
Yes, but there were several reasons for the normally-energized series line systems. Another thing is that telegraph "lines" might indeed be a single wire.. Using the Ground as the "Return" for the loop This was often done both for telegraph and for mains electrical at one time due to a shortage of metal for the wires... This is very likely why house systems have a ground bonded to the neutral at the service entrance AND AT THE POLE.. At one time they simply forgot to use a neutral. Plus I"ve seen several "Loop" systems today where a single wire is looped from the "Central office" out to each "node" or station and all the way back.. One such was made by Phillips back in 1980.. I used to be one of the operators (This was a telephone system) the finished product, I used to joke, had one part that NEVER FAILED... That was a reset button... The original failed and the replacement came from Radio Shack. |
#3
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generating morse code
On Apr 16, 10:20 am, John from Detroit wrote:
N2EY wrote: Yes, but there were several reasons for the normally-energized series line systems. Another thing is that telegraph "lines" might indeed be a single wire.. Using the Ground as the "Return" for the loop It is my understanding that many of them were. Besides the savings in wire and insulators, a ground-return system could actually be lower resistance than a double-wire system if the "made grounds" at the ends of the lines were very good. Of course such a line is more vulnerable to noise, but since the wire telegraph was a digital system the nouse would have to be considerable to have any effect. 73 de Jim, N2EY |
#4
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generating morse code
N2EY wrote:
On Apr 16, 10:20 am, John from Detroit wrote: N2EY wrote: Yes, but there were several reasons for the normally-energized series line systems. Another thing is that telegraph "lines" might indeed be a single wire.. Using the Ground as the "Return" for the loop It is my understanding that many of them were. Besides the savings in wire and insulators, a ground-return system could actually be lower resistance than a double-wire system if the "made grounds" at the ends of the lines were very good. Of course such a line is more vulnerable to noise, but since the wire telegraph was a digital system the nouse would have to be considerable to have any effect. That thing about noise reminded me of a story about a severe magnetic storm that happened in the 1880s or thereabouts. Currents induced into telegraph lines were so strong that things caught fire in telegraph offices as well as simply knocking them offline. -- David Griffith --- Put my last name where it belongs |
#5
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generating morse code
David Griffith wrote:
N2EY wrote: On Apr 16, 10:20 am, John from Detroit wrote: N2EY wrote: Yes, but there were several reasons for the normally-energized series line systems. Another thing is that telegraph "lines" might indeed be a single wire.. Using the Ground as the "Return" for the loop It is my understanding that many of them were. Besides the savings in wire and insulators, a ground-return system could actually be lower resistance than a double-wire system if the "made grounds" at the ends of the lines were very good. Of course such a line is more vulnerable to noise, but since the wire telegraph was a digital system the nouse would have to be considerable to have any effect. That thing about noise reminded me of a story about a severe magnetic storm that happened in the 1880s or thereabouts. Currents induced into telegraph lines were so strong that things caught fire in telegraph offices as well as simply knocking them offline. Friend of mine hooked a very high impedance volt meter to his long wire antenna one storm and got some very interesting voltmeter readings Several volts (As in 3 digits) as I recall.. Of course it did not take much current to ground it out but it was amazing the amount of voltage on that wire. My Long wire is DC-Grounded so I don't see that. |
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