AT&T Archives: A Modern Aladdin's Lamp, about vacuum tubes,1940

hello milk still holding the fort I see are you George haven't seen you around in a long time this is Bill Miller the chief of our transmitter season no mr. Thomas tried annoy you mr. Miller how do you do mr. Thomas is quite an event for us to have a broadcast from here this is a special one on vacuum tubes bill how about showing him some real work oh sure thing look right over here take a look in there mr. Thomas that's where your a voice covering they stepped up before it goes out into the ether low it's a whopper isn't it they're among the largest tubes made mr. Thomas they handled so much power that they have to be cooled by a circulating water system yes sir if it weren't for these babies there wouldn't be any radial then worse yet bill and I'd be out of a job but yes and a million others owe their jobs to the vacuum tube including myself as a matter of fact practically everybody has been benefited by it in some way my broadcast begins with 25 years ago in New York Alexander Graham Bell repeated the first words ever transmitted by telephone mr. Watson come here I want you but this time the inventors assistant laughs I can't make it under a week dr. Bell I'm in San Francisco it was the first transcontinental telephone conversation this exchange of greeting marked the opening of transcontinental telephony the same year soft speech transmitted across the Atlantic by the first radio telephone yet both of these miracles of communication developed from a single discovery the vacuum Chu a discovery which spun from a chance observation in this workshop of a great inventor at Menlo Park New Jersey the story begins in 1883 with trouble the breaking of the filaments of Thomas Edison's incandescent lamp observing that the break invariably occurred at the positive end of the filament Edison reasoned that some unknown negative electrical particles were bombarding this end of the hot wire further experiments revealed that the flow of charged particles could be influenced by an extra wire sealed into the bulb of the leg Edison recorded this curious phenomenon in his notebook and turned to his many other inventions it became known as the interesting but useless Edison effect a generation later dr. lee deforest added a third element which transformed the edison effect into a bottle of magic the first vacuum Jew but it remained for Bell Telephone laboratories scientists and engineers to perfect and commercialize the vacuum tube notable among this host of researchers for Western Electric and the Bell System where doctors Jewett Colpitts Vanderbilt and the late dr. Arnold with their colleagues they developed the tube into a commercial sensation and then in a hundred specialized forms they applied it to the facilities of electrical communication thus from this product of the Bell Laboratories grew four great new industries long-distance telephony radio the modern phonograph and the sound motion picture industries can you recall the telephone of a generation ago New York to Denver was the longest call that could be made and it was uncertain then the vacuum tube went into service and the transcontinental telephone became a reality line spread to every city and town and hamlet in the country radio telephones spanned every ocean connecting the telephone in your home with 38 million of the world's 40 million telephones all because of vacuum jeux can amplify the human voice without distortion the product of this magic lamp we call a vacuum tube is not light but electricity electrons set free from the atoms of matter that hold them captive and the world and all it contains are built of atoms yet hidden in every single last atom is from one to ninety-two electrons this wire like everything else is composed of atoms and if microscopes could magnify 10 million times instead of paltry thousands one of these atoms probably would appear as a tiny elastic sphere a sphere formed by negatively charged electrons swarming around a massive nucleus of positive electricity some substances especially metals do not keep their electrons tightly bound to the individual atoms but allow them to roam around aimlessly between the atoms in the interior of the substance such substances are called electrical conductors because if a battery is connected to the ends of a wire made of such a substance the free electrons drift along the wire continuing their aimless motions as they drift it is this mass movement of electrons that we call an electric current whenever the aimless motion of an electron carries it past the surface of the metal into the space outside it is immediately pulled back by the electric attractions between the electron and the atom community it has less to become useful in a vacuum tube however these electrons must be separated from their atom communities and allowed to move alone this we do by heating the wire with an electric current the atoms and electrons become increasingly agitated until some of the electrons rush at the surfaces of the wire at high-speed speed so high they could flash from New York to Detroit in one second at these speeds electrons are able to break through the electric forces which try to restrain them they escape to move about in space outside the wire now if we set up a nearby target of positive electricity the electrons which escape from the surface of the wire are pulled directly to the plate actually however the space between the wire and plate is jam-packed with gyrating air atoms literally billions of them and to reach the plate the electrons would have to bulk their way through them like midgets in the subway crowd and many of the electrons would be pulled into strange atoms on the way this problem is solved by enclosing the wire and plate in a glass bowl then a vacuum is created by pumping out every possible air atom and right here is where we get to named vacuum tube now the negative electrons shoot straight at the positive plate without interference this pulling of electrons from atoms isn't done for amusement on the contrary it's an important economic problem research to date has increased many fold the number of electrons that can be freed for ascent and each year this little item alone saves us about 12 million dollars on power bills to run our radio sets here is how it was done research revealed that some atoms give up their electrons more willingly than others so the engineers devised coatings for vacuum tube filaments these coatings produce surfaces which permit electrons to escape at comparatively low temperatures in this way the power required to heat the filament is substantially reduced now with but a trickle of current the improved film barely glows yet away from each square inch of it's hot surface flow more than ten trillion electrons a second the positive plate the cube second element is completed by adding an outgoing wire control however is lacking needed is a traffic cop on the electronic Highway and this is the job of the vacuum tubes third element or electrode the grid and with its introduction begins the real utility of the tube made negative to repel the negative electrons flowing from the filament each increase or decrease of voltage applied to it let's few our many electrons pass to the plate or should you prefer an Arabian Nights technique these are ours monkeys throwing pebbles at a target through a shutter a plea portray what goes on in a vacuum tube simple isn't it yet it's the essence of one of the world's most important discoveries ability of the electronic vacuum tube to amplify or control any sort of electrical wave motion puts a hundred million new tubes to work each year yet if we know how they are used in telephony we can understand their function in all speech transmission apparatus to reproduce the human voice across the United States with our vacuum tubes and telephone lines would require about 150 thousand hog callers spaced within earshot the time entailed more than five hours the telephone does it better in a twelfth of a second and instead of hog callers it uses repeater stations 40 or more dotting the speech highway for instance between New York and San Francisco inside our banks of vacuum tube amplifiers repeater tubes the telephone engineers call them tubes in each repeater station function on every long-distance call amplifying the voice each way here's how it's done vibrating under the impact of sound waves the transmitter diaphragm starts a pulsating movement of electrons along the wire but as the energy of the electrons is gradually used up enforcing those ahead into light pulsations the voice current becomes weaker by the mile entering the grid in feeble waves the voice current is nevertheless ample to mold the electrons flowing from the filament into a similar wave pattern reenergized without distortion the voice current now speeds from the plate and jus arriving at the receiver with just the right strength to reproduce the original sound waves how much is your voice amplified by these repeater stations between New York and San Francisco you say it I can't the figure is 10 with 99 zeroes after it yet the voice sounds are neither louder nor softer when they arrive than they were when they start for these magic lamps amplify enough to exactly offset the energy lost on the way regardless of the merit of an invention or discovery it achieves greatness only when it contributes to the well-being of many people this is the role of Western Electric and like organizations the mission of making such inventions as the vacuum tube available to all of us theirs is the exacting business of building into each product the qualities of long life dependability and operating efficiency here in the Western Electric vacuum tube plant each operator is a skilled craftsman a trained specialist in his or her particular task this painstaking care and manufacture has earned for the telephone repeater and its sister tubes the unique distinction of being custom-made typical is the making of repeater choose the vacuum tubes used in long-distance telephony they begin their long life in this automatic buck cut flare machine long lengths of glass tubing are cut into pieces and carefully flared to size at each end each piece destined for use in the glass foundation of a Chu the prepared flares are here drawn out at one end to receive the spaced lead-in wires the flares prepared and formed are now put on metal supports in which the ledian wires have been inserted then this stem making machine whirls the glass and metal combination through the carefully spaced and sized jets of burning gas and through automatic pressing jaws into an annealer it last delivers a complete glass foundation or stem a stem gas-tight free from strains with lead-in wires exactly sized and spaced for the mounting of kube electrodes the uniformity of Western Electric tubes is largely due to the precise work of this automatic grid winding machine it holds two heavy wires which serve as Grid supports not just them to secure the small grid windings whines the finer wire in place then hammers the notches over the windings spacings between windings are uniform to a few millionths of an inch and the operation is concluded without stretching or deforming any of the wires from rolls of carbon coated nickel sheet this carefully guarded punch press turns out halves of plate sections the plate halves are next fastened together by a sort of metal stitching called staking the resulting electrode the plate which catches the electrons in the completed jus is accurate in its dimensions to a few thousandths of an inch the vital third element of the vacuum tube the filament is begun in annealing and coating machines metal ribbon the core material is drawn without stretching through heated tunnels and over pulleys and guides until the chemical coating is completely applied running with perfect synchronization this machine cleans the filament ribbons in the heated tube on top and returns them through three chemical coating bags throughout this entire process the chemical composition of the coating and the dimensions of the coated film are controlled to the closest limits the elements of the tube are its glass foundation its filament grid and plate together with some supporting pieces and these are all brought together in the assembly position on accurately machine jigs they are fitted into each other and securely fastened in place by electric welding adjusted for each weld the welding machine delivers precisely the amount of electrical energy required to make the metals flow together to obtain a secure joint completed the tube structure is accurate within microscopic limits in all its spacings none of the parts are distorted in the least as a result of the assembly and yet the finished product is sufficiently rugged to withstand ordinary handling both during subsequent manufacture and in shipment and use at this point the complete assembly is sealed into a glass bowl the assembly is held in the revolving head of a gas-fired machine the bulb is put over it and then the bottom of the bulb is cut away by melting at a point where bulb and stem can be securely fused together the completed seal in as it is called is gas tight and free from strains or leaks or other defects on this automatic exhaust machine the tube becomes a vacuum tube for all gases are drawn from it with vacuum pumps operating full-blast that you be swept into a tunnel where it is heated electrically to a degree just short of melting the glass this drives all impurities out of the glass envelope and the tube elements and down into the pumps at this point the base is fitted over the lead-in wires these are clipped and bent into position and the tube is sent through a gas-fired tunnel to fasten the base to the glass by high temperature cementing from the basing machine goes to the soldering position here the leaves are soldered to the sides of the metal projections that make the contacts between the two elements and the telephone circuit in which it is to be used each based and soldered tube now goes into an aging soffit and receives full load operating voltages for 8 to 16 hours and at the end of this stabilizing treatment it is tested for uniformity stability and serviceability and finally the repeater tube is carefully cleaned it is now ready for use but even here insistence on manufacturing perfection is manifested in the sample tubes picked at random from the production line for special tests and life runs and in these files are kept the records of each of these sample tubes records which show that these tubes will operate over 50,000 hours and still perform at top efficiency here are the tubes which give voice to radio and talking pictures cubes that enable the public-address system to speak to thousands and the telephone user to talk across continents and built into all of them are the endurance and high performance of the telephone repeaters from those no larger than a peanut - this 100 kilowatt jaw and giant 250 kilowatt vacuum tubes the biggest broadcasting tubes in the world yes Cube making in this plant is more than a manufacturing process it's an art and the men and women you have seen our artisans artisans who translate the achievements of research into the qualities inherent in all Western Electric vacuum tube in distant earth quake or bringing an elevator level with the floor wherever you find the vacuum tube working its magic we'll be promoting your security and comfort and convenience all in flight 14 ok 14 weather at terminal ceiling unlimited then scattered cloud at fiber at B visibility 5 miles with northeast 17 miles there is only one course and that course begins with a decision that the rights of man liberty and justice are in the United States to stay I know mother I'm phoning from the ship we're a thousand miles at sea okay headquarters car 60 on the way to Lee Avenue call got me a radio compass bearing on that SOS bring it up all of these things and more are happening every day happening because of a single product of Industrial Research and while it was girdling the earth with speech the vacuum tube added billions to our national income raised our standard of living produced numberless new conveniences from it developed great and small new industries the network of long-distance telephony radio broadcasting high fidelity recorded music talking motion pictures this magic lamp has created a million jobs in every city and town and village in the country jobs in service and manufacture jobs in entertainment and education it has built a thousand factories open ten thousand stores and shops created vast demands for the raw materials of farms and mines and forests all these things and more happened because of a single product of individual enterprise and the American Way of life and so long as they endure there will be no end to the miracles of this modern Aladdin's lamp the vacuum juice you you

Channel: AT&T Tech Channel

Views: 355,020

Rating: 4.933567 out of 5

Keywords: Vacuum Tube (Invention), history, AT&T (Business Operation), AT&T Archives, Lee De Forest (Author), western electric, amplifier, Transistor (Invention), Broadcasting (Industry), Documentary, 1940, Radio (Invention), telephone

Id: _-JzxX75oYc

Length: 21min 32sec (1292 seconds)

Published: Tue Apr 29 2014

Reddit Comments

[u/Chicken-n-Waffles]

"Like midgets in a subway crowd"

Golden at around the 7 minute mark.