Relays, Keys, Registers and Sounders.
By Franklin L. Pope
From : The Telegrapher, July 27, 1872
I found this rare article in the Western Union Archives at the National Museum of American History. It was written by Franklin Pope who was a respected and influential telegraph engineer and author, and a frequent contributor to the popular 19th century telegraph magazine, "The Telegrapher". This article is one of the earliest accounts on the development of telegraph instruments in the U.S. and provides a snapshot of its progress as of 1872. Pope also gives a different account of the inventors responsible for improvements made to telegraph instruments than what has been previously documented by some contemporary authors. I felt it was important that his article should be republished and made available to readers today. The comments in italics are mine.....J. Casale |
From that time forward improvements have constantly been made in different portions of the apparatus and mechanism. The cumbrous relays first employed were soon replaced by others of more reasonable size. (James) Clark, of Philadelphia, first constructed a relay with the horizontal magnet, which has maintained its supremacy to the present day as the favorite and accepted type of the American relay. Morris Hall introduced the movable magnet, for facilitating the adjustment - an improvement which has since been almost universally adopted. G. M. Phelps covered the coils with hard rubber cases, and contrived a method of mounting the magnet which, for simplicity, convenience and durability, it is safe to say will not soon be excelled.
The first important modification in keys was the substitution of the rigid lever sounder (a straight key lever) with a spring and circuit closer for the strap key (strip of sheet brass) and wedge. The lever was the idea of Thomas C. Avery. Alfred Vail suggested the adjustable screw stops, and Henry J. Rogers combined the whole into a practical and convenient instrument, by mounting the lever upon an arbor between adjustable centres. Mr. Rogers's key, which was made under his direction by Mr. James Green, was substantially the Morse key of to-day. Subsequently the key and circuit closer were combined together, different manufacturers using different devices for this purpose. The spring, or "snapping" circuit closer, so common at the present day, originated in the Caton shop, at Ottawa, Ill.
This is an enlarged image of the left hand side of the "Telegrapher" masthead. The Morse register referred to in the article is shown on the bottom left. It also shows instruments of the other two competing systems in the U.S. during the 1840s. The printing telegraph of Royal House and the chemical telegraph of Alexander Bain. |
Tradition is silent respecting the birthplace of the original sounder. It would not be hazardous to assert, however, that it was nothing more than a superannuated register, "razeed" by some ingenious operator. The little "pony" sounder, of which not less than six thousand are clicking within the limits of the United States as these words are written, was invented by A. S. Chubbuck, of Utica, N.Y., and not a few operators still think that no one else can make them to sound quite as well.
All things considered, there is very little choice between the different patterns of instruments produced by either one of half a dozen of the best manufacturers in this country. It is perhaps as much a matter of taste and personal preference as anything else that influences the decision. In the elegance and appropriateness of their designs our manufacturers are confessedly superior to their European rivals, while in excellence of workmanship they fall little, if any, behind them. If they do not surpass them in the latter respect, also, it is only for the reason that the prices purchasers are generally willing to pay are as yet not sufficient to justify the production of articles of the highest possible degree of excellence. It is noticeable, however, that there is of late a marked tendency towards the use of a better class of apparatus, and an increased willingness to pay the difference in cost entailed thereby.
A person familiar with the practical manipulation of telegraphic apparatus can scarcely, however, have failed to become aware of the fact that there is still much room for improvement in some of the minor details of the instruments constructed at the present day. In connection with what has been said, a few suggestions upon this subject may perhaps not be out of place : There has been a very general tendency, within the last two or three years, to reduce the resistance of telegraphic relays. This is a reform in the right direction when not carried too far, as it has been in some instances. If it were absolutely necessary to equip every line with one standard relay, probably nothing would give better average results than a uniform resistance of about 150 ohms or Siemens units. This is rather high for a crowded railroad or city wire, and too low for a long through circuit with few instruments. Most of the relays now made measure from 100 to 150 units. In reducing the resistance, however, much better results would have been obtained by simply increasing the size and conductivity of the wire, instead of retaining the fine wire and reducing the size of the cores and helices. Experiment proves that a relay, with coils 3 inches long by 1 1/2 inches diameter, and half inch cores, will work much stronger and better on a given circuit than one with coils 1 1/4 inches long and 1 inch diameter with 3/8 inch cores, and having precisely the same resistance. Relays of the latter dimensions are, notwithstanding, coming into very general use. A large share of their popularity is doubtless due to their small size and neat appearance. Both the manufacturers and purchasers of relays are now fully awake to the importance of using none but the best iron and the purest copper wire in their construction, so that nothing need be said on this score. A fact not so generally known was pointed out some years since by Mr. G. W. Dean, of the U.S. Coast Survey, who proved, by repeated experiments, that a longitudinal groove cut in each core of a relay, extending from the centre to the circumference, will cause it to charge and discharge with much greater facility, or, in other words, to "follow up" more quickly. This is an important improvement, and is worthy of general adoption. (This longitudinal groove cut into the core of the electromagnet was used by Thomas Edison in several of his Quadruplex and printer designs later this decade. Pope was a business partner with Edison a few years before this article was written. )
Keys, as they are now and always have been made, are liable to become defective in two or three different ways: The lever is very apt to become loose on the arbor in the hands of many operators who "send" with a heavy side motion. It has been suggested, as a remedy for this, to have the lever cast either in the form of a cross or of a hollow rhomboid, usually known as a "diamond" shape. This would give the arbor a much longer bearing, and probably make a much better key. (Nine years later, Franklin Pope was the patent attorney for Jesse Bunnell's Steel Lever Key patent. This lever design became an industry standard and is still recognized today as being cast in the form of a cross.) The perfect circuit closer is yet a thing of the future. The brass lever sliding between two flat brass discs becomes worn by use so as to fail to perform its office, and it is no uncommon circumstance for the spring circuit closer to become deranged, so as to leave the circuit open about the thousandth part of an inch. What makes the matter worse in both the above cases is, that to all appearance the circuit may be firmly closed, as far as the key is concerned, and yet be open. There is certainly an ample opportunity for inventors to improve on the arrangements now in use.
Most of the sounders now made have one fault, which, although quite a serious annoyance, is fortunately capable of being very easily removed. The nut which controls the tension or the retracting spring ought to be double. It is almost always mad single, and in nine cases out of ten cannot be made to stay in place, owing to the constant vibration of the sounder.
One of the most prolific sources of difficulty in and about instruments is the American style of binding post. To any telegrapher of experience, its numerous and serious defects are sufficiently obvious. It constantly tends to work itself loose, and always succeeds in doing it sooner or later if left alone a sufficient length of time. The hole for the thumb-screw is seldom bored exactly to the proper depth. Sometimes it is too short, reaching only to the line (a) (see Fig. 1). In this case it is impossible for it to hold a small wire firmly, and the same trouble is frequently experienced with larger wires. Another post will, perhaps, be bored down to the line (c), the result of which is that the screw cuts off or breaks the wire, leaving either a very shaky connection or, quite as often, none at all, though everything appears to be all right, looking at the outside.
These posts are usually fastened to the base of the instrument by a machine screw, (s),
provided with a washer, (w), underneath which the connecting wire is inserted. This arrangement
is continually getting loose in consequence of the shrinkage of the wood, and very frequently
gives rise to an imperfect connection, or not connection at all, between the washer and the loop
of the wire. All the connections between the wires and binding posts of telegraph instruments
ought to be soldered, but this is very seldom attended to, and much trouble and interruption arises
in consequence. One of the best arrangements for a binding post that has ever been devised is
that shown in Fig. 2. The upright stem (d) projects upwards from a base, (f) ; the wire is placed
at (k)and looped closely around the stem (d); then the nut (h) is screwed down upon the loop and fastened by the lock-nut (g). The whole is secured to the wooden base of the instrument by two screws, (m) and (n), passing through a single washer, (o). The connecting wire should be passed around (m) and (n)and well soldered.It would be well if practical operators would occasionally call attention to the defects of the instruments with which they work, and suggest means of avoiding them is any such should occur to them. The mechanicians who design and construct telegraphic apparatus not being, as a rule, practical operators, cannot reasonably be expected to foresee and provide against all the contingencies that arise in practice from different forms and modes of construction, but they may doubtless be led to adopt such modifications and improvements as may be found, after discussion and experiment, to be advantageous or desirable.
To learn more about Franklin Pope, please visit - Franklin Pope : Telegraphic and Electrical Engineer
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