[LB021122], Letter from Thomas Alva Edison to Alfred Ord Tate, November 19th, 1885


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[LB021122], Letter from Thomas Alva Edison to Alfred Ord Tate, November 19th, 1885

Editor's Notes

I find it impossible for me to leave New York just now as I am very busy. In fact, I hardly think I will be able to get to Toronto at all. ##I shall send you tomorrow three phone receivers. There is a pen in the center of the diaphragm upon which is a weight. When a sharp noise comes, the weight pumps up and in coming back makes the down stroke. The next wave makes the up stroke. To make the up stroke weaker, I put in a small{?} resistance on the down point so that when the lever leaves the down point to make the upstroke, the battery{?} is weaker away to the four little spools inserted in the branch running to the down point. The amount of condenser is best ascertained when you get your own writing strongest. The phone is put right in the casing{?} itself. There is an adjusting screw on the bottom where you can adjust the magnet{?} to and from the diaphragm.This {------} works left-handed. Where the phone current is very weak, a very light weight is used. Where it is strong, a heavier weight can be used. We sent you some different weights for experimental purposes. I find this magnetic{?} phone, while not as sensitive as the motograph, works very satisfactorily on a line One Hundred and twenty{?} five miles long (distance emphasized}. I have now tested it four nights between new York and Boston on a copper wire grounded at each end with induction so strong that they are unable to work it (the lines) with a telephone (for talking) when grounded, but have to use metallic {-------} to enable them to talk. This current is 300 miles long, but its equivalent in No. 8 {---------} wire is 120 miles. It works perfectly satisfactorily over this distance, therefore do not attempt to phonoplex a line longer than from 120 to 125 miles with this new apparatus. You will find that it is not near as {sensitive?} to outside induction as was the motograph. Be careful when you work to have the magnets as close to the diaphragm as they will stand without sticking. This you can readily ascertain by adjusting while the distant man is writing. Use four cells of gas and carbon battery on the phone {-------}. Be careful that every relay in the line has got a condenser on it. Should there be a relay at some test office unknown to you this would almost wipe out the phone on account if its self discharge. Be sure that every magnet has a condenser round it on the line and be sure that they do not plug in an extra instrument at the {-------} Station. If you desire to try this on a line from Toronto to Montreal and if they still work{?} morse from Montreal to Toronto while you are on phonoplex from Toronto one hundred miles out, do as follows. {-------} all the keys and relays of the Morse apparatus at all {underlined} the stations from Toronto one hundred miles out, but never mind shutting{?} beyond that. Now at the last station at the end of the hundred miles, put in an extra relay beyond the phonoplex and Morse apparatuses. Then take two condensers; put the end of one condenser on the side of the magnet pointing towards Toronto and the other end of that condenser to the earth. Now at the other side of the magnet pointing toward Montreal, put another condenser, with the other end to the ground as shown in diagram No. 2. Put 48 sheets in each of these condensers. You want to use the heaviest weight on the phone that you possibly can to get the writing because the heavier the weight which will still do the work, the greater the induction impulse must be to lift it. Thus you see you can work the phone on this Montreal wire without interfering with the through traffic. However, you had better try it grounded first.





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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University
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