[D8736ACT], Letter from Postal Telegraph Cable Co, Francis W Jones to Samuel Insull, July 9th, 1887


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"In reply to your favor of 21st ult. I beg to say that my present object is to satisfy myself of the feasibility of using dynamos in our present circumstances. As we are not permanently located, the plan, if practicable, may not be adopted at present. I wish to know if it is as economical to run a bank of dynamos for telegraph purposes, in series, as it is independently, this, [diagram drawn here in the middle of the typed letter] the current to be used being the same in each case, and further, can shunt machines be used in both cases or must separate exciters be employed. What resistance would the 400 volt machine have, that is the joint of armature and shunt when running and about the speed? If not too much trouble, I should like this information as to each dynamo, both in series and independently. (I mean by series, dynamos in series.) ## As to insurance, the Company must have current day and night. Do you favor the use of steam from the Steam Company's pipes, with a Gas engine in reserve, and to give the various potentials would an extra dynamo be necessary for each potential in independent? We have about 200 wires long and short, and average resistance say of 2000 ohms, and would probably desire to provide for double this with a large margin to spare. One half of the wires would require x and the other --" Marginalia by TAE: brief notations related to the technical questions asked by Francis W. Jones about telegraphy.









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[D8736ACT], Letter from Postal Telegraph Cable Co, Francis W Jones to Samuel Insull, July 9th, 1887

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