Beardslee Signal Corps Telegraph Limitations




The Beardslee telegraph used by the Signal Corps in the Civil War has been described as both a success and a failure. All agreed that taken as a whole system utilizing light lances, insulated wire and reels, it was the most deployable communications system capable of operation in all weather and over all terrain. This was clearly demonstrated by the USMT use of the deployment system when it took over the overall system in late 1863. Although I do not have at hand the primary source documents proving that the Signal Corps tried to connect standard keys and sounders to the wire system they controlled, the rumor persists and appears in many secondary documents. The political reasons for this development will be the subject of another investigation. I intend to focus on the technical aspects of the Beardslee system that defined how it operated and what its limitations would have been. We will also postulate what it could have been based on the state of the art as known then and what aspects of that state of the art that could be derived from George Beardslee's patents.

First of all let us understand the timeframe we are working with. Today, we tend to view the development of military equipment as an orderly movement from theory through prototype to deployed tool with rational follow-on modifications or improvements coming from field experience or parallel technology developments. We also see this development through the prism of government sponsored and funded research with the research and development component much removed from the day to day operations of the battlefield. In short, we expect scientists, engineers and technologists in lab coats patiently developing and testing equipments to be later fielded and refined.

The real case, up until the Second World War, was that much of this work, when done at all, was done by intelligent and gifted individuals working within (and often against) the military organization itself. Often these individuals made considerable contributions without holding high rank. Often these men would be lieutenants, Captains and Majors where today they would be Colonels and Generals in similar positions. Myers as a Major, who had personal wealth through marriage, developed the nascent Signal Corps. Major Armstrong of the Signal Corps was the father of the regenerative receiver, the super-regenerative receiver, the superhetrodyne receiver and the FM receiver and transmitter. At higher rank, General Squire of the Signal Corps developed carrier multiplexing which led directly to the sending of multiple telegraph and telephones circuits over a single wire or radio carrier. This also led to the development of Muzak under General Squire's direction. It is note worthy that each of these men collided with the forces of avarice. Myer was nearly crushed by the telegraph establishment. Squire found his inventions, which he wished to be used for the good of all, taken by AT&T after ugly legal battles. Armstrong's regenerative circuit was challenged by DeForest and resulted in a long legal battle that ultimately resulted in the theft of the rights by the ruling of an ignorant and un-teachable judge. The superhetrodyne became the backbone of the radio and television industry and is used in nearly all sets today. The FM system was bitterly contested by some twenty-one companies. Although his widow won the lawsuits in the end, he had already killed himself by putting on his hat and coat and stepping out of his New York hotel window in 1954.

You may be asking why what purports to be a semi-technical analysis would begin with this sort of history. In short, nothing like the research facilities of Fort Monmouth or the MIT Radiation Laboratory existed in 1861 to develop and protect Signal Corps equipments from the greed of the commercial interests, provide the necessary incubation environment, funding the modifications found necessary in field equipments or shield the inventions from political interventions. Major Myer, like those who followed him, stood alone against all forces and had but little resources beyond his own considerable intellect, personal funds, and wits to bring to bear. He was further burdened by having to do all of this during the most desperate war this country had known in several generations.

Let us now turn to the technical limitations of the Beardslee. These can be broadly broken down as 1) a slow rate of transmission, 2) an error rate considered to be higher than the magnetic telegraph and, 3) a very limited transmission range. In truth, these are all inter-related to a high degree.


Slow Rate of Transmission


In the first case, where the Beardslee was considered to be capable of only a slow rate of transmission, it is guilty as charged. The dial consists of thirty positions around the circumference. In the worst case of a double letter, all thirty positions must be traversed to send the second iteration. Setting aside all other factors and accepting this worst-case analysis as the baseline, we are left with an analysis of the advancing mechanism. This mechanism is an escapement very similar as would be found in a pendulum driven clock. Each advance would require two movements of the escapement. Each movement would advance the dial six degrees with twelve degrees per step being 360/30. Thus we would need sixty movements.

Through experiments with the drives, I have determined that 200 milliseconds to be approximately the maximum speed such a drive would operate without missing a "beat". If we assume that the advance time might also require a like period of time to reverse, we can see that the range of actuation per twelve degrees would be between 400 and 600 milliseconds. Taking the mean and multiplying by thirty would yield a rotation time of fifteen seconds. The normal number of letters considered to be a word for the purposes of such a calculation has, over time, been established to be five letters per "word". Thus we can calculate that the "words per minute" or "WPM" would be 5 multiplied by 15 divided by 60. This is 1.25 WPM. Even if we half the possible advance time we have a maximum speed of 2.5 WPM. If we move from the worst-case situation to the average of fifteen steps between letters, we still can only come up with 5 WPM. Add to this the fact that the operator must stop at each letter to allow its selection to be noted by the distant end and assume that this time is at least three seconds, we are left with a speed of about 4 WPM. Take your pick of numbers, but you are not likely to drive the system much over 5 WPM under any circumstances.

Contrast this with a "typical" Morse operator who would consider 5 WPM as the speed one who has just learned the code would most likely be capable of sending and receiving. A reasonable operator would consider 10 WPM as the bottom end of the range defining a competent operator with 20 WPM being the "top of the middle". Experts would be operating in the 25 to 35 WPM range on good circuits. It is simply much easier to move an iron lever up and down using one or two electromagnets than it is to convert that motion into circular rotation with thirty possible positions. Pick your own numbers: Still guilty as charged.

But, let us put that into context. Torch and flag signals were no faster. Weather and smoke were also major factors as to whether communication took place at all. Also, if you review the telegrams sent during the bulk of the war, you will find some pretty wordy notes replete with "Major Blither sends his most sincere compliments to Colonel Inebriate and is pleased to respond to his communication of Tuesday instant….. I remain, sir, your ob't servant, etc. etc.". The use of Signal Corps developed stutter and brevity codes that converted into "plain English" before the final delivery, seems to have been less used on the higher speed telegraph circuits at least until Petersburg. One could assume that the differences in the actual bulk weight of the message for a given intent tended to balance the issue.

This, of course, assumes that the telegraphic abbreviations were not fully developed as a set yet. Some such sets may well have existed and were in use at some point during the war-- most likely during the Petersburg era. However, in the case of Gettysburg where the USMT did not show up at all until after the battle or at Fredericksburg, where the river precluded bare wire telegraph operations, the point was moot.

Ironically, a close review of George Beardslee's patents show that he was just a thought or two away from taking his magneto design and refining it into a stepping motor and replacing the escapement. This would have improved the speed of the machine. But, to be fair, this would have required him to build two of his magnetos into a stack and come up with the necessary relays to drive it. Furthermore, it is unlikely given the scales (largely dictated by the power of the magnets and the size required which would be massive) he would have had to work with; the speed could have been much more than doubled.

But, it is an intriguing idea that almost certainly would have been explored had a research facility in the modern sense been tasked to examine the overall device and desired functionality within the constraints of the patents.


High Error Rate



The Beardslee Telegraph sends a single pulse over the wire to indicate that an advance of the dial is required. One might argue that two pulses are available given the voltage reversal. But, that would ignore the fact that both are needed to cause a single advance of the escapement. So, it is really one pulse. The good news is that should someone attempt to tap into the lines and read the signals, they would have to know or extrapolate the position of the dial from the pulse trains. The stop for letters and word positions would have no discernable differences than the stops at the letters. The task would not have been impossible, but time consuming. Also, information learned in any "decoded" message would prove of limited value in "decoding" any subsequent messages. The bad news is that the loss or addition of a single pulse would cause the dial to fall back or jump ahead.

Of course this could be corrected by an astute receive operator who was following the message content. Upon realizing that the message just "went gibberish" he would open the circuit briefly. The transmit operator would see his pointer no longer following his dial turns and would cease sending and switch to receive and set his pointer to the start position. The receive operator would then set his pointer to start and send the last word clearly understood and switch back to receive. The transmit operator would then pick up where the failure occurred and then continue on. This is not that different from the telegraphic opening of the circuit, quick break-in click or long dash to gain attention followed by AB for all before or AA for all after and the last clearly received word.

Where it would become problematic is in that instance where the message sent over the Beardslee was not in clear language, but had been put into cipher. Knowing that any code group was or was not correct would not be easy. Only the word count and the use of five letter groups would give a clue. Morse signals, having distinct codes for each character did not accumulate errors. An error was generally contained within a signal letter with the following letter containing all of the information needed to decode it. Beardslee signals had no such stop on the accumulation of error. Each letter had exactly the same information as the last representing it. Only its position relative to the last was significant. If that was lost, only knowledge of the "sense" of the message would allow re-construction.

One might argue that this was also the case on the Morse circuits. But, in addition to the discrete code containted within each character sent, there are very subtle signals being decoded by the ear along with the actual code being sent. First of all, there is the code itself. Each letter had it's own symbol as part of a well-known set. You knew that an A was this and B was that. Anything other than what you knew to be part of the valid set of codes had to be an error. Timing flow was also a clue. A click between words or an extra long pause were signs that an error might have occurred. A butchered letter in plain or clear (unencrypted) text could and would be simply filled in by the receiving operator. The system also provided feedback to the sending operator. He or she could hear an error, recognize it, send a string of dots (usually eight) indicating and error was just sent and back up to the point where the error was perceived to have occurred and restart the transmission. Of course, this option was open to the Beardslee operator as well, but generally he was not as well trained or confident as a seasoned Morse operator would have been. Myer assumed that merely sending the manual back and forth once was sufficent training.

The operator's "fist" was also very important. Experienced operators knew who was on the line from the characteristics of their sending methods without resort to the "sine" or "sign" or "call-sign". These were due to key type, grip, timing faults or quirks, speed-up or speed-down, swinging the key and other factors that while small, taken together defined the signal as being unique. Changes in that pattern were also an indication that something went wrong. This along with the word count in five letter groups (the check) served as a pretty fair system of feedback. With the Beardslee, you were simply one level removed from these other clues. So we can conclude that the Beardslee was less capable of indicating errors where the text itself could not be easily read as either right or wrong when compared with the Morse telegraph system but completely capable of error correction where the text was "plain" or "in the clear". Furthermore, we must recognize that the men operating this equipment were not themselves stupid nor did stupid men lead them. One can easily conjure up a sense that a "control" five letter code group might be inserted in the message at pre-concerted lengths of transmission to serve as clues as to loss of synchronization. No evidence exists that they did this at any time, however. Furthermore, there is no evidence that the Signal Corps ever felt the need to encript Beardslee transmissions. There would be no need, in my opinion. Thus, the source of the "prone to errors" charge must be found elsewhere. This in spite of the obvious lack of specific knowledge to the device itself as to what any given signal pulse might or might not mean at any given time.

We should mention the issue of security while we still dwell on the pulse information content. The Beardslee, when sending "in the clear" was much more secure than the Morse system sending the same message. This is precisely because of the lack of information respecting what a pulse means, the fact that one or more stop points can be used and it's operational area could be expected to be heavily infused with friendly troops. One does not simply "tap" and listen in without having another Beardslee or something very similar. We must remember that in spite of what the USMT would have said, the Beardslee was always intended to link the army commander with his corps and to link, at the edges of the battlefield the flag and torch system as needed. No claim was made to supercede the long-haul commercial lines by the Signal Corps. It was thus less exposed to the tender mercies of the horse soldiers. It was, as Myer claimed, more likely to be cut by the common soldier due to its novelty and proximity.


Limited Transmission Range



We now come to what must be considered the crux of the matter: the complaint of limited range for the Beardslee. There are two main factors to consider. First there is the issue of the wire diameter and composition. The second is the magneto itself.

The wire itself has been described as being composed of "thin" copper wire from France with a rubber coating. While I have but one source that describes the wire as thin and from France, many sources mention the particular aspect of the rubber coating. The link to Conrad Popenhusen of College Park, New York was almost certainly due to his ownership of a rubber works and George Beardslee's residence there. His company most likely provided the rubber coating for the imported wire. It was through this association that he apparently was awarded the contract to produce the Beardslee telegraph itself.

But what of this wire? We do not know the gauge of the wire-only that it was "thin". Since the source of this comment was a signal officer, we must assume that he knew what "normal" telegraph wire was and that this might be thinner. The samples I have collected range from fourteen gauge to something like nineteen gauge. Both iron and copper. For the sake of discussion, let us assume that the gauge was smaller than fourteen or nineteen. I will assume twenty-four gauge. This, in copper, will yield a resistance per mile of about 150 ohms. We will make a further assumption that the wire used in the escapement vibrator is thirty-six gauge and consists of about a thousand feet of copper. This gives a coil resistance of about 450-600 ohms. The opposing coils would be in parallel. Let's call the termination resistance as being 250 ohms. Another assumption is that about six volts will actuate the vibrator. This would be a fairly reasonable .024 ampere of current.

To get a ten mile range we need thirty-six volts drop across the 1,500 ohm line resistance and an additional six volts or so for the coils. This is a total of about 42 volts output from the magneto. This is not an unreasonable output for a magneto of the design we are looking at. There are six poles and the gearing (1:5 then 1:2 over thirty steps) ratio will cause a pulse (positive then negative--or mark/space for a single advance) to be generated each time a letter is passed through roughly its middle position on the dial. Similar magnet sizes dating to the approximate timeframe (we have to make this kind of assumption as the magnet piles in the surviving Beardslee telegraph have certainly lost their magnetism--so we will assume that the magnetos used in telephone circuits in the 1880's would be very similar and, perhaps, a bit better) generated up to 90 volts output peak. So, 45 to 90 volts would not be out of the question for a maximum output. One engineer on the Beardslee project is quite certain that the output voltage could have even peaked up two or three times that. lacking a governer on the magneto, it would be unwise to think this impossible. For another view of this same calculation see the updated insulated wire question and answer page.

So why did the Beardslee have the reputation of being a five mile machine? Even by the most conservative estimate it should have been able to handle ten miles without any concern. Something must be lowering the useable voltage.

That something is time. The magneto is capable of developing a particular voltage when cranked or turned. But the real story is that for a given pass over the wire spool a magnet will cause a certain amount of power to be output. No more and no less. This power is the output pulse. If I turn the dial rapidly the magneto poles will pass over the wire spools (coils) fairly fast. The energy or power that the magnet and coil combination is capable of producing will be concentrated in a short period of time. Since power (in watts) is the current squared times the voltage and the load (in amps) remains fixed for a particular circuit (.024 amp in our example--ignoring counter EMF from the coils and the capacity between the wire line and the ground. We will assume that they cancel for the purpose) then a fairly high voltage and current will be output. Now if I slow up the dial to a crawl, we are still going to output the same amount of power into the load. But now this power is distributed over a longer period of time. The voltage and current output is much lower. But, the power remains the same. Here is the heart of the matter: to get the best range, you must turn the dial quickly so as to generate the highest voltage. But if you turn the dial too fast, the vibrator driven escapement moving the pointer will not be able to make its movements and the pointer will fall behind the dial crank. If the range is only five miles or so, then the "sweet spot" speed for the dial had to have been where about fifteen volts was output. Go faster and the pointer will not keep up. Go slower and your maximum range is diminished. Worse, it is a square function. It should be obvious that at the limits of the range, real care had to be taken by the operator to ensure a consistent speed that was just below the tracking speed of the escapement vibrators. Add a second escapement to the mixture and you are looking at a very difficult task. Dave Harbin points out that trying to simply select the letter next to the one you just selected was very difficult in its own right. The slow movement would not allow maximum output. The operators would find that going full circle around was the best way to avoid loss of the next letter under these circumstances. He also points out that the inertia of the magneto pile would lead to a very delicate touch being required to just "sneak up" on a letter. This would cause a grave tendency to over shoot--itself a source of errors. Field tests with the replica Beardslee sets bears this out. The majority of errors are the cause of overshoot. The lack of "DETENT" at any given letter stop is just another "feedback" failure.

If we consider that the second escapement and possibly two more were in the circuit, the voltage needed would, in the first case double and in the second quadruple. This quickly puts us up into the one to two hundred-volt range for reliable communication at ten or more miles.

What Could Have Been Done?

Let us assume that Myer and Beardslee had the luxury of a test ground other than the battlefield. Let us further assume that they had access to the existing telegraphic technology and could use it without being blocked by the commercial telegraph companies. It is not likely that these companies would have allowed him to use so much as a battery. The fact that he used rubber coated copper wire when the industry used bare wire allowed him to be "allowed" to use wire at all. Things could have been much different. First of all, they could have increased the wire diameter. This could have been done by either paralleling the existing wire or ordering up heavier wire for the spools. Paralleling the wire would have doubled the effective range. Going to sixteen gauge copper would have lowered the resistance per mile to about 25 ohms. This alone would have increased the operating range to about 30 miles and the maximum range to 60 miles. I suspect that when the USMT took over the "flying telegraph" and mated it with their own instruments, they found that they needed around 100 volts to make it work well; this even with their sensitive and highly adjustable instruments. Such would have been the effect of the small gauge wire.

The next thing that could have been done was to accept the need for a small local battery such as a ten-cell set of Daniel cells for an output of 10.2 volts. This would be isolated from the line with a (say 400 ohm) relay. The adjustments of the relay would ensure that marginal voltages could be worked with. The local voltage would have eliminated the high degree of variability in terms of voltage present to the vibrator escapement coils.

The best modification, in our estimation, would to have been to add detents. This would provide visual, aural and tactile FEEDBACK to the operator. The equipment simply required that the operator develop the "touch" to an extent that was beyond Major Myer's claim that anyone could just "use" the machine.

Going to use WD-1? Here are the Specs.


WD-1 is 243 Ohms per mile with ground return and 486 ohms per mile in wire loop.

AWG American Wire Gauge / Diameter / Resistance

AWG  Diameter  Diameter  Square  Resistance  Resistance 
  mm  inch    mm2  ohm/km  ohm/1000 feet 
46 0,04 0,0013 13700
44 0,05 0,0020 8750
42 0,06 0,0028 6070
41 0,07 0,0039 4460
40 0,08 0,0050 3420
39 0,09 0,0064 2700
38 0,10 0,0040 0,0078 2190
37 0,11 0,0045 0,0095 1810
36 0,13 0.005 0,013 1300 445
35 0,14 0,0056 0,015 1120
34 0,16 0.0063 0,020 844 280
33 0,18 0,0071 0,026 676
AWG  Diameter  Diameter  Square  Resistance  Resistance 
  mm  inch    mm2  ohm/km  ohm/1000feet 
32 0,20 0.008 0,031 547 174
30 0,25 0.01 0,049 351 113
28 0,33 0.013 0,08 232.0 70.8
27 0,46 0.018 0,096 178 54.4
26 0,41 0.016 0,13 137 43.6
25 0,45 0,0179 0,16 108
24 0,51 0.02 0,20 87,5 27.3
22 0,64 0.025 0,33 51,7 16.8
20 0,81 0.032 0,50 34,1 10.5
18 1,02 0.04 0,78 21,9 6.6
16 1,29 0.051 1,3 13,0 4.2
14 1,63 0.064 2,0 8,54 2.6
AWG  Diameter  Diameter  Square  Resistance  Resistance 
  mm  inch    mm2  ohm/km  ohm/1000feet 
13 1,80 0,0720 2,6 6,76
12 2,05 0.081 3,3 5.4 1.7
10 2.59 0.102 5.26 3.4 1.0
8 3.73 0.147 8.00 2.2 0.67
6 4.67 0.184 13.6 1.5 0.47
4 5.90 0.232 21.73 0.8 0.24
2 7.42 0.292 34.65 0.5 0.15
1 8.33 0.328 43.42 0.4 0.12
0 9.35 0.368 55.10 0.31 0.096
00 10.52 0.414 69.46 0.25 0.077
000 11.79 0.464 83.23 0.2 0.062
0000 13.26 0.522 107.30 0.16 0.049



Metric Gauge  Diameter  Square  Resistance 
  mm    mm2  ohm/m 
5 0,5 0,20 0,0838
6 0,6 0,28 0,0582
8 0,8 0,5 0,0328
10 1,0 0,8 0,0210
14 1,4 1,54 0,0107
16 1,6 2,0 0,00819
20 2,0 3,14 0,00524
25 2,5 4,91 0,00335


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