If you'd like to see pictures of the hardware and some of the history that goes along with this:(Unfortunately you have to download the whole 2.5 MB PDF presentation; look for the two or three slides on either side of the one that says "A Nobel in the noise . . . ")
(Same presentation but with half-size slides and the speaker's notes.)
One of the few fundamental physical phenomena the measurement of which was impeded by, among other things, bird poop.
This wasn't the first time that someone measuring noise at Bell Labs had made a fundamental physical discovery. Physicists these days, and even electrical engineers, often call it "Nyquist noise": e_n^ 2 = 4 kTRB in the classical limit.
But in fact it was a Bell Labs engineer, J. R. Johnson, trying to track down the source of noise in early triode amplifiers, who observed that some of this noise seemed to come from the grid bias resistor.
So he performed extensive experiments using all kinds of different resistances (carbon, wire wound, even some liquid-cell resistors, at different temperatures); and concluded that they all seemed to contain a universal noise source
e_n^ 2 ? 4.0 (+/- 0.07) kTRB
After he published a lengthy, total experimental paper on this: J. R. Johnson, "Thermal agitation of electricity in conductors," Phys. Rev., vol. 32, pp. 97--109, 1928.
his Bell Labs colleague wrote a brief, remarkably simple quantum derivation of the same result, in its full quantum form. H. Nyquist, "Thermal agitation of electric charge in conductors," Phys. Rev., vol. 32, pp. 110--113, 1928.
and laid the basis for pretty much all of our understanding of thermal noise, circuit noise, maser and laser noise, and their connections to thermodynamics and blackbody radiation today.
In my first response I pointed out an earlier, related, and also quite fundamental discovery at Bell Labs made almost eighty years ago; and cited the references J. R. Johnson, "Thermal agitation of electricity in conductors," Phys. Rev., vol. 32, pp. 97--109, 1928.  H. Nyquist, "Thermal agitation of electric charge in conductors," Phys. Rev., vol. 32, pp. 110--113, 1928.
Just to push this a little further, if you want to read these early Phys Rev papers you can go to the American Physical Society's "PROLA" web site and download copies of these classic early Bell Labs contributions for free.
In fact, the _entire_ massive print run of Phys Rev all the way back to Vol. 1, No. 1, in _1893_ is available on line at this site.
But suppose you want to read about some of the Bell Labs work which laid the foundations for the forty year ago accomplishment that Lisa Minter has (very justifiably) noted above; two of them are R. W. DeGrasse, E. O. Schulz-DuBois, and H. E. D. Scovil, "The three-level solid state traveling wave maser," Bell Sys. Tech. J., vol. 38, pp. 305--335, 1959.  A. B. Crawford, D. C. Hogg, and L. E. Hunt, "Project Echo: A horn antenna for space communication," Bell Sys. Tech. J., pp. 1095--1099, 1961.
Well, the Bell System Technical Journal (BSTJ) -- which in its full print run since 1928 has presented not just these papers, but numerous fundamental papers on the invention of waveguides, Shannon's communication theory, North's fundamental noise and signal theory papers, important early papers in quantum theory and chemistry, many fundamental papers on lasers including all the pioneering papers on laser resonators, and many others -- IS NOT AVAILABLE ON LINE, IN SCANNED OR ELECTRONIC FORM, ANYWHERE.
Trying to get this situation changed has been one of my pet hobby horses for some time. If any telecom readers and/or Bell Labs alumni have any way to help make it happen, it would be very much worth doing.[TELECOM Digest Editor's Note: If you are able to make this happen, I'd feel honored to make them part of the Telecom Archives files, as was done with the Western Union Tech Review files. PAT]