The Invention of the First Wearable Computer
Edward O. Thorp
Edward O. Thorp & Associates
EOThorp@ix.netcom.com

Abstract
The first wearable computer was conceived in 1955
by the author to predict roulette, culminating in a joint
effort at M.I.T. with Claude Shannon in 1960-61. The
final operating version was tested in Shannon’s basement
home lab in June of 1961. The cigarette pack sizedanalog device yielded an expected gain of +44% when
betting on the most favored “octant.”
The Shannons and Thorps tested the computer in Las
Vegas in the summer of 1961. The predictions there wereconsistent with the laboratory expected gain of 44% but aminor hardware problem deferred sustained serious
betting.
We kept the method and the existence of the computer
secret until 1966.

1: The idea: 1955
In the spring of 1955 while finishing my second yearof graduate physics at U.C.L.A., I thought about whether
it was possible to beat the roulette wheel. A theorem saidno mathematical system existed. What about biased(defective) wheels? Al Hibbs and Roy Walford had
successfully and sensationally exploited one in Reno in
1949-50, but wheels now usually do not have exploitable
imperfections [14]. I believed that roulette wheels weremechanically well made and well maintained. With that,the orbiting roulette ball suddenly seemed like a planet inits stately, precise and predictable path.
I set to work with the idea of measuring the positionand velocity of the ball and rotor to predict their future
paths and from this where the ball would stop.
Such a system requires that bets be placed after theball and rotor are set in motion. Thus the casinos have aperfect countermeasure: forbid bets after the ball islaunched. However, I have checked games throughout theworld and rarely were bets forbidden after the ball was
launched. A common practice instead was to call “nomore bets” a revolution or two before the ball dropped
into the center. The simple casino countermeasure meantthat in addition to predicting, one must conceal thesystem.
For camouflage I planned to have an observer near
the wheel recording numbers that came up, as part of a“system.” This is common and doesn’t seem out of place.
But the observer would also wear a concealed computer
and time the ball and rotor. (Later we used toe-operated
switches, leaving both hands free and in the open.) The
computer would send the prediction by radio to the bettor
who, at the far end of the layout, would appear unrelated
to the observer-timer. The bettor would have a poor viewof ball and rotor and would not pay much attention tothem. To further separate timer and bettor, I would haveseveral of each, with identical devices. They would eachcome and go “at random.”
A bettor who only bet after the ball was launched, andwho consistently won, would soon become suspect. To
avoid that, I planned to have the bettor also make bets
before the ball was launched. These would be limited sotheir negative expectation didn’t cancel all the positive
expectation of the other bets.

2: First Efforts: 1955-60
I began work late in 1955. Confident of the idea, I
started on the radio link concurrently with physics
experiments. Then I studied a cheap half scale wheel bymaking movies of the wheel in action, and to time eachframe the picture included a stopwatch that measured inhundredths of a second. By studying the film and plotting
orbits from this data, I learned that my wheel and ballwere very irregular and that their defects prevented
predictability. But full-sized wheels were not like that. In
December 1958, partly to study real casino wheels, I mademy trip. I observed several wheels and found that the ball
moved smoothly in its track. When I saw how good thecasino wheels were, I believed that prediction was
possible. But now I needed a full-sized wheel and somegood laboratory equipment.
Ironically, on this same trip, I happened to try out arecently published blackjack strategy by Baldwin et al [1].
This led quickly to the idea for a winning blackjack card
counting system and I set to work intensely. Then in
March or April of 1959, twelve man years of blackjackcalculations arrived, courtesy of Baldwin et al and I put
the roulette project aside.
In the summer of 1959 I moved from U.C.L.A. to
M.I.T. where I wrote my blackjack computer programs.
By mid 1960 I had the basic results for the five-countsystem, most of the ten-count system and the ultimate
strategy. I also worked out the methodology leading totoday’s “one parameter” blackjack systems. Fear ofplagiarism and worse (fulfilled) led me to seek quick
publication. I chose the Proceedings of the National
Academy of Sciences. Needing a member of the
Academy to communicate my paper, I sought out the only
mathematics member at M.I.T., Claude Shannon.
I arranged an appointment early one chilly November
afternoon. But the secretary warned me that Shannon was
only going to be in for a few minutes, not to expect more,
and that he didn’t spend time on subjects (or people) that
didn’t interest him.
Feeling awed and lucky, I arrived at Shannon’s office
to find a thinnish alert man of middle height and build,somewhat sharp featured. His eyes had a genial crinkle
and the brows suggested puckish incisive humor. I told
the blackjack story briefly and showed him my paper.
Shannon was impressed with the results and method
and cross-examined me in detail, both to understand andto find possible flaws. When my few minutes were up, hepointed out in closing that I appeared to have made thebig theoretical breakthrough on the subject and that what
remained to be discovered would be more in the way ofdetails and elaboration. We changed the title from “A
Winning Strategy for Blackjack” to “A Favorable Strategy
for Twenty-One” (more sedate and respectable). I
reluctantly accepted some suggestions for condensation,
and we agreed that I’d send him the retyped revision rightaway to forward to the Academy [5]. And then he asked,“Are you working on anything else in the gambling area?”
I decided to spill my other big secret and told him
about roulette. Ideas about the project flew between us.
Several exciting hours later, as the wintery sky turned
dusky, we finally broke off with plans to meet again onroulette.

3: Teaming up with Claude Shannon
Shannon lived in a huge old three story wooden house
once owned by Jane Addams on one of the Mystic Lakes,
several miles from Cambridge. His basement was agadgeteer’s paradise. It had perhaps a hundred thousand
dollars (about six hundred thousand 1998 dollars) worthof electronic, electrical and mechanical items. There were
hundreds of mechanical and electrical categories, such as
motors, transistors, switches, pulleys, gears, condensers,
transformers, and on and on. As a boy science was myplayground and I spent much of my time building andexperimenting in electronics, physics and chemistry, andnow I had met the ultimate gadgeteer.
Our work continued there. We ordered a regulation
roulette wheel from Reno for $1,500 and assembled otherequipment including a strobe light and a large clock with asecond hand that made one revolution per second. The
dial was divided into hundredths of a second and finer
time divisions could be estimated closely. We set up shop
in “the billiard room,” where a massive old dusty slatebilliard table made a perfect solid platform for the roulette
wheel.

3.1:

Analyzing the motion

The plan was to divide the various motions of balland rotor into the following simpler stages and analyzeeach separately:• The croupier launched the ball. It orbits on ahorizontally oriented circular track on the stator, slowing
until it falls from this (sloped) track towards the centerrotor. Assume first that (a) the wheel is perfectly level,and (b), the velocity of the ball determines how many
revolutions it has left before falling off. Then the time for
one revolution of the ball would determine how many
revolutions and how much time remained until the ball left
the track.
• Next analyze the ball orbit from the time the ballleaves the track until it crosses from the stator to the rotor.
If the wheel is perfectly level and there are no obstacles,
then it seems plausible that this would always take thesame amount of time. (We later learned that wheels areoften significantly tilted. This tilt can affect the analysis
substantially. We eventually learned how to use it to ouradvantage.)
There are, however, vanes, obstacles, or deflectors on
this portion of the wheel. The size, number, andarrangement vary from wheel to wheel. On average,
perhaps half the time these have a significant effect on theball.
• Assume the rotor is stationary (not true), and predictthat situation first. Even a stationary rotor introduces
uncertainty due to the ball being “spattered” either
backward or forward by the frets (the dividers between thenumbered pockets). Thus successful physical prediction
can at best forecast with an advantage a sector where theball will stop.
• Next, assume the rotor is spinning. The ball androtor are spun in opposite directions increasing theirrelative velocity. This increases the number of relative
revolutions and “stretches” the forecast probability
distribution, decreasing predictability. A moving rotor
also increases “spattering.” On a given spin, friction slows
the rotor very gradually, so one can accurately predict its
position when the ball leaves the track.

I will now sketch what we did.

3.2:

Timing errors

First, consider the ball moving on the track.
To predict when and where on the stator the ballwould leave the track, we timed one ball revolution. If thetime were “short,” the ball was “fast” and had a longer
way to go. If the time were “long,” the ball was “slow”
and would fall from the track sooner. We hit a
microswitch and started the electronic clock as the ballpassed a reference mark on the stator. (Actual casino
wheels have many such marks.) When the ball passed thereference mark again we hit the switch, stopping the clock
and noting the time for this revolution.
The clock switch also flashed a strobe, which“stopped” the ball each time the switch was hit. This
showed how much the ball missed the reference mark.
Since we knew the ball velocity, we could tell about how
much we were early or late in hitting the switch. This let
us correct times recorded on the clock, making the datamuch more accurate. The visual feedback also trained us
to become much better at timing.
With practice our timing errors fell from r.m.s. valuesof about 0.03 seconds to about 0.01 seconds. Later wetrained our big toes to operate switches in our shoes anddo almost as well.
The total prediction error comes not only from timing
but from approximating the complex dynamics of thesystem, from the “spattering” of the ball on the rotor
pocket dividers (frets), the deflection of the ball by metal
obstacles as it spirals down the stator, and the possible tiltof the wheel. Assuming the total error was approximately
normally distributed, we needed a standard derivation of
about 16 pockets ( ± 0.42 revolutions) or less to get
positive expectation both for best single number and best
octant bets. We actually achieved an expectation of about
44% for the best single number and about 43% for thebest octant, corresponding to a standard derivation of
about 10 pockets or ± 0.26 revolutions.

3.3 A time of fun and ferment
We worked from November 1960 to June of 1961
designing and building the computer. Shannon was atreasury of intriguing information and ingenious ideas. In
discussing the need for secrecy he mentioned that social
network theorists studying the spread of rumors claimed
that two people chosen at random in, say, the UnitedStates are usually linked by three or fewer acquaintancesor “three degrees of separation.” I tested this then andlater, with several remarkable confirmations. A June 1998
New York Times Science Times article attributed thedegrees of separation idea to a sociologist in 1967. Yet it
was well known to Shannon in 1960.
For bet sizing in favorable games, Shannon suggested
I look at a 1956 paper by Kelly [3]. I did and adapted it
as our guide for blackjack and roulette, and used it later inother favorable games, sports betting, and the stock
market [9, 13]. The principle was to bet to maximize theexpected value of the logarithm of wealth. This has
desirable properties that are discussed in detail in thereferences.
The Kelly strategy traded a little expectation for alarge reduction in risk by diversifying over several (good)numbers. From this and Shannon’s observation that instimulus - response experiments with n choices (e.g. see alight or hear a tone and then make one of n choices) the
response time seems to follow the rule a+b ln n, we
settled on “octants.”
As we worked and during breaks, Shannon was anendless source of playful ingenuity and entertainment. He
taught me to juggle three balls (in the ′70’s he proved“Shannon’s juggling theorem”) and he rode a unicycle ona “tightrope,” which was a steel cable about 40 feet longstrung between two tree stumps. He later reached his
goal, which was to juggle the balls while riding theunicycle on the tightrope. Gadgets and “toys” wereeverywhere. He had a mechanical coin tosser which could
be set to flip the coin through a set number of revolutions,producing a head or tail according to the setting. As ajoke, he built a mechanical finger in the kitchen which wasconnected to the basement lab. A pull on the cable curled
the finger in a summons. Claude also had a swing about
35 feet long attached to a huge tree, on a slope. We
started the swing from uphill and the downhill end of thearc could be as much as 15 or 20 feet above the ground.
Claude’s neighbors on the Mystic lake wereoccasionally astounded to see a figure “walking on thewater.” It was me using a pair of Claude’s huge
styrofoam “shoes” designed just for this.
One day I walked into his study to find a cryptic
211=2048 on the blackboard. He had been buying hot
IPOs in a raging up-market and doubling his money
monthly. He also had been profiting greatly frominsightful early stock purchases in local high techcompanies.
Shannon seemed to think with “ideas” more than withwords or formulas. A new problem was like a sculptor’s
block of stone and Shannon’s ideas chiseled away the
obstacles until an approximate solution emerged like animage, which he proceeded to refine as desired with moreideas. It was Shannon’s remarkable mind that impressedme most.

4: Design and construction: 1961

Consideration of a wide range of designs led us to a
final version of the computer which had twelve transistors
and was the size of a pack of cigarettes. Our big toes
input data with microswitches in our shoes. One switch
initialized the computer and the other timed the rotor andthe ball. Once the rotor was timed, the computertransmitted a musical scale whose eight tones marked therotor octants passing the reference mark. The computerwas “set” earlier to match the wheel and ball and to
optimize prediction for a selected number of ballrevolutions to go. We usually chose the range between 3
and 4 revolutions. When the timing switch was first hit
for the ball, the tone sequence shifted and played faster.
As the timing switch clocked the ball for the second time,
the tones stopped and the last tone heard named the octant
on which to bet. If the timer misjudged the number of ballrevolutions left, the tones continued indicating no
prediction. Since the prediction, if sent, was simultaneouswith the last input, the compute time was zero.
We each heard the musical output through a tiny
loudspeaker in one ear canal. We painted the wires
connecting the computer and the speaker to match ourskin and hair and affixed them with “spirit gum.” Thewires were the diameter of a hair to make theminconspicuous but even the hair thin steel wire we used
was fragile. The first time I was fully wired up for arehearsal in the lab, Shannon cocked his head and with atwinkle in his eyes asked, “What makes you tick?”
In April of 1961 I went to Nevada with Mr. X andMr. Y and successfully tested my blackjack system [6, 7].
I also observed roulette wheels secretly and confirmedthat they behaved like our lab wheel. Further, many ofthem were tilted, a feature which could further improveprediction.

5: The computer in Las Vegas: 1961
The wearable version of the computer was complete
and operational in June of 1961. In the summer of 1961
the Shannons and Thorps met in Las Vegas for a casino
test. We used ten cent chips and often turned a few dimes
into a pile as yet another octant “hit.”
When thecomputer was working, it worked very well.
Claude generally stood by the wheel and timed, andfor camouflage recorded numbers like just another“system” player. I placed bets at the far end of the layout
where I paid little attention to the ball and rotor. We
acted unacquainted. The wives monitored the operation,
checking to see whether the casino suspected anything and
if we were inconspicuous. Once a lady next to me looked
over in horror. I left the table quickly and discovered the
speaker peering from my ear canal like an alien insect.
Claude and Betty and my wife Vivian were nervous
whereas I wasn’t, perhaps because my blackjack trip

familiarized me with the scene. In retrospect they wereright, judging from the Mafia riddled “gaming” industryof the time, accurately shown in the recent movie“Casino.”The wires to the speaker broke often, leading totedious repairs and the need to rewire ourselves. This
stopped us from serious betting on this trip. Except for
the wire problem, the computer was a success. We could
solve this with larger wires and by growing hair to cover
our ears, a conspicuous style at the time, or persuade ourreluctant wives to “wire up.” We adjourned to consider.

6: Afterward: 1962-98
An attractive offer took me from M.I.T. in June of1961 and for reasons such as the difficulties of working
together at a distance and the opportunity cost from ourother activities, we never continued the project. In 1961 I
also built a “knockoff” to predict the “wheel of fortune” or“money wheel” [4]. It used the toe switch for input, thespeaker for output, a single unijunction transistor andrequired only one person. The matchbox sized computer
had an expected gain of more than 200% in the casinos
but the game had too little action to conceal the late bets
and the spectacular consequences.
Finally in 1966, I publicly announced our roulettesystem [8] because it was clear now that we weren’t going
to exploit it. More details appeared in [10, 11, 12].
Around 1969 a member of the future Eudaemonic Piegroup called and I outlined our work and results in detail.
They went on to build an operational wearable roulettecomputer in the ′70’s using the next generation oftechnology.
They also reported a 44% positive
expectation but were ultimately frustrated by hardware
difficulties [2]. Other groups also launched secret roulette
projects, several of which (including the “Romeo
Project”) reportedly led to substantial casino wins.
Shannon and I discussed building a simple wearable
blackjack computer but I found mental card counting
easier so we passed. However, Keith Taft and others built
and marketed them. Finally on May 30, 1985 the Nevada
devices law was signed into law as an emergency measure.
The target was blackjack and roulette devices. The law
banned use or possession of any device to predict
outcomes, analyze probabilities of occurrence, analyze
strategy for playing or betting, and keeping track of cards
played. The descendants of the first wearable computerwere formidable enough to be outlawed.

7: References[1] R. Baldwin, W. Cantey, H. Maisel, and J. McDermott, “The
Optimum Strategy in Blackjack,” Journal of the American
Statistical Association, Vol. 51, 1956, pp. 429-439.

[2] T.A. Bass, The Endaemonic Pie, Houghton Mifflin, New
York, 1985.
[3] J.L. Kelly, “A New Interpretation of Information Rate,” Bell
System Technical Journal, Vol. 35, 1956, pp. 917-926.
[4] P. O’Neil, “The Professor Who Breaks the Bank,” Life,
March 27, 1964, pp. 80-91.
[5] E.O. Thorp, “A Favorable Strategy for Twenty-One,”
Proceedings of the National Academy of Sciences, vol. 47, No.
1, 1961, pp. 110-112.
[6] E.O. Thorp, “A Prof Beats the Gamblers,” The Atlantic
Monthly, June, 1962.
[7] E.O. Thorp, Beat The Dealer, Random House, New York,1962.
[8] E.O. Thorp, Beat The Dealer, 2nd Edition, Vintage, New
York, 1966.

[9] E.O. Thorp, “Optimal Gambling Systems for Favorable
Games,” Review of the International Statistical Institute, Vol.
37, 1969, pp. 273-293.
[10] E.O. Thorp, “Systems for Roulette I,” Gambling Times,
January/February 1979.
[11] E.O. Thorp, “Physical Prediction of Roulette I, II, III, IV,”
Gambling Times, May, July, August, October 1979.
[12] E.O. Thorp, The Mathematics of Gambling, Lyle Stuart,
Secaucus, New Jersey, 1984.
[13] E.O. Thorp, “The Kelly Criterion in Blackjack, Sports
Betting, and the Stock Market,” Finding the Edge:
Mathematical Analysis of Casino Games, Vancura, Eadington
and Cornelius, editors, Univ. of Nev., Reno, 1998, to appear.
[14] A. Wilson, The Casino Gambler’s Guide, Harper andRow, New York, 1965.