This rather eye-catching device is a handheld Tesla bulb from a Fischer diathermy machine, a sort of quack medical device consisting of a Tesla coil wrapped in Bakelite and medical make-believe. The tube itself consists of a two chambered envelope with a disk shaped electrode surrounded by an unknown purple gas. The second chamber of the tube is filled with normal air and is shaped into a handle; this allows an operator to manipulate the tube over a patient without being shocked themselves. A single electrode on the top of the tube allows it to be attached to the console of the diathermy machine by means of a cloth wire. The gas fill used in this probe is at a much higher pressure than what is typically found in a Geissler tube or Tesla bulb, which is what causes the unusual ribbon-shaped discharge seen around the center disk.

It should be noted that some limited applications of diathermy, such as radio frequency cauterization techniques for surgery, have legitimate medical use. However, it is a far stretch from this to imagine that waving a glorified neon bulb over a patient will cure cancer, as advocates of diathermy regularly claim.

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"Crookes Tube" is the generic descriptor given to a wide range of hard vacuum demonstration devices, each with a different educational function. This particular tube, also known as a "beam deflection tube" was designed to illustrate how a cathode ray beam could be deflected by a magnet. A thin beam of cathode rays is projected through the slit at one end of the tube and strikes a slanted metal plate, which has been covered with a phosphor to produce a visible line discharge. When a magnet is brought near the tube, the effect of the magnetic field can be seen in the deflection of the cathode ray beam.

Though traditionally cathode ray tubes of this type were pumped down to a vacuum state, the example shown here is a newer gas filled version, most likely made during the 1950s. To make it easier to strike the tube with lower voltage supplies, this example has been filled with hydrogen, which is what produces the blue discharge at either end of the tube.

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A Tesla bulb is a type of early cold cathode light source, one which appears to have never entered commercial production. First built and demonstrated by Nikola Tesla in 1892, a Tesla bulb's defining feature is a total lack of electrodes that penetrate the glass envelope. Instead, a high frequency power supply is used to energize the bulb externally, typically through a graphite or foil conductor that extends through a small glass tube into the center of the bulb. The bulb shown here is a reproduction; unfortunately it appears no original bulbs have survived into the present day. The bulb consists of an evacuated chamber, filled with residual low pressure water vapor, which is penetrated by a tubular glass passage to allow the conductor to reach the center of the bulb. The brightness of the bulb varies considerably once it warms up; the water vapor fill gas will condense into the surface of the glass and must be 'boiled off' for the bulb to reach full intensity. The lack of electrodes penetrating the glass envelope makes a Tesla bulb immune to one of the most common failure modes of other electron tubes; air leakage at the glass-to-metal boundary of the tube's pins. Power requirements are much more complex however; Tesla bulbs require a Tesla coil or some other form of high voltage pulsed power source that can project enough energy through the glass envelope to ionize the tube's fill gas. This was a serious problem in 1892 given the level of technology available, fortunately, the modern experimenter can use a violet ray wand or BD10 high voltage supply to easily activate an electrodeless tube such as this.

It should be noted that Tesla bulbs intended for light output likely included a phosphorescent coating on the inside of the outer globe, which would convert the high voltage discharge into a more usable shade of light. Patent drawings also suggest the final version of the bulb intended for residential use contained a single electrode wire connected to a carbon button in the center of the envelope, which likely lowered the power requirements to ionize the water vapor considerably. Though it is common to consider the Tesla bulb a direct predecessor to the modern florescent tube, florescent tubes contain heated filaments and are in many ways closely descended from the tungsten filament lamps that were in production in the 1930s. Tesla bulbs do have a modern descendant however; the decorative plasma globe. Though the typical plasma globe is filled with high pressure neon instead of low pressure water vapor, the construction and power supply requirements are otherwise almost identical.

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This rather obscure Crookes tube is designed to demonstrate the phosphorescent properties of various minerals, in this case calcite, when exposed to an electron beam. The center of the tube contains a cubical sample of calcite caged within the embrace of a bent glass rod. A large plate electrode at the top of the tube generates a cone of electrons that excite the calcite and cause it to glow red. The glow of the calcite is persistent; the sample will continue to emit light for several minutes after power has been removed from the tube. Originally this tube would have been mounted to a turned wooden stand by means of the long glass extension exiting below the calcite sample; a century of human friction stripped this example from it's stand long ago. Based on the tube's cap construction and the way in which the calcite sample is mounted, it is likely this particular tube was made late in the 19th century.

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Sometimes tube collectors come across something truly bizarre. This strange device is a Crookes tube which contains a large glass eye under a tangle of filament wire. Both the glass eye and the containing tube are filled with argon, a small internal pinhole connects the two chambers of the tube. When high voltage is passed between the two electrodes of the tube, the gas discharge causes UV sensitive glass in the iris of the glass eye to glow. This very strange tube is a modern creation, and was manufactured by the glassblower Dylan Kehde Roelofs sometime prior to 2016.

Suffice to say, collectors should not confuse a mutant organism such as this with the much more common Magic Eye tuning indicator tube. No radio known has ever used this thing as a tuning indicator, and if one did, it could likely only be used to communicate with Cenobites and other extradimensional beings.

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A De La Rive apparatus is a specialized gas discharge device designed to demonstrate that the glow discharge in a low pressure environment can be influenced by electromagnetic fields. The De La Rive apparatus consists of two parts, a low vacuum electron tube with a tubular depression passing through it's radius, and an electromagnet that mates to the tube such that the electromagnet's core passes through the center of the tube. When the tube is activated and a voltage is passed across the electromagnet, the discharge beam will rotate around the ring-shaped anode in the same direction as the magnetic field, demonstrating that the glow discharge is made up of charged particles that can be influenced by an external electromagnetic force.

This example, manufactured by Electro Technic Products, was probably produced sometime in the mid 20th century as an educational demonstration for high school and college physics classes. Interestingly, the control coil for this example is made out of the re-purposed shell of an Electro Technic BD10 violet ray generator, a device commonly used as a sex toy amongst more adventurous members of the human population.

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The Geissler tube is an electrical demonstration device that was invented in 1857 by Heinrich Geissler. Starting in the 1880s, Geissler tubes were mass-produced as functionally useless decorative devices, designed to provide entertainment to wealthy Victorians, and such tubes could arguably considered to be the world's first electronic entertainment product. Technically, a Geissler tube is simply an evacuated glass tube with two electrodes, which has been filled with a noble gas or other substance to produce a demonstrational glow discharge. In practice however, Geissler tubes are usually highly decorated, formed into complex shapes and encrusted with whorls of uranium glass and liquid filled cavities.

This example is a fairly representative of the typical form of a Geissler tube; it is constructed of two glass spirals connected to glass bubbles at each end which contain the electrodes. The center 'grape' bubble of the tube is made out of uranium glass, and fluoresces green when the tube is under high tension.

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This is a post WW2 Geissler tube that was manufactured specifically for the educational market. Though most Geissler tubes are typically highly decorated, this particular example is somewhat unusual due to its completely unshaped and undecorated envelope, which was designed to allow students to observe the flow of the gas discharge under different external magnetic and electrical fields. This can be seen in the photo to the right, the 'dark space' at each electrode is clearly visible, as are the standing waves produced by the high frequency power supply used for the photo. Though this tube was sold by Welch Scientific, we are almost certain it was actually manufactured by Electro-Technic Products sometime between 1960 and 1980 based on it's shape and electrode construction.

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Devices included in this entry:

Argon spectrum tube (glass capillary vessel)
Krypton spectrum tube (glass capillary vessel, pictured in thumbnail)

Here is an example of a set of spectrum tubes with unusually shaped envelopes. These tubes have right angle electrodes like the "H" shaped tube above, but add the extra attachment of a globe shaped discharge chamber at one end of the capillary vessel. This construction style allows the tube to serve double duty as both a capillary emitter and a point spectral source.

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Up until fairly recently, Crookes tubes were rather expensive devices. A high school or college physics instructor looking to use a Crookes tube in a classroom demonstration would either be forced to buy an expensive reproduction from a scientific supply house, or hope to find an original tube left behind by some long dead Gilded Age researcher. For this reason many teachers resorted to building their own Crookes tubes from whatever glassware and raw materials were on hand. The example shown here is one such device, and serves as a visual example of how sketchy a homemade Crookes tube could be. The tube body is constructed from the outer shell of a Liebig condenser, which has had its thistle removed and replaced with two rubber stoppers. One stopper serves as the cathode, while the anode has been threaded through a blob of resin and bent into a hook which holds a single vane made out of plastic. In operation the stream of cathode rays released by the bottom electrode would strike the plastic target and, hopefully, make it move in response. This tube was designed to be hooked to a vacuum pump continuously while in operation; its resin and rubber construction is likely far too leaky to hold a decent vacuum for any length of time.

The recent arrival of cheap Chinese reproduction Crookes tubes have likely made crude devices such as this wholly obsolete.

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The Sylvania 1B59 is a gas-filled glow modulator tube that was used primarily in early fax machines and military imaging devices. Operating on the same principles as a hollow cathode lamp, the 1B59 produces a concentrated blue-orange spot of light that is projected out of the tube's flat front window. When attached to a moving carriage or mounted in front of a rotating mirror, this point of light can be used to draw images on photosensitive paper. The 1B59 has an operating voltage of 140 volts and can be switched on and off at speeds of up to 15kHz. This tube was made in several different variants, with some versions of the tube being packaged in a more traditional rounded T9 octal envelope covered in a black paint overlay. The 1B59 is believed to have been released sometime around 1946.

One noteworthy use of the Sylvania 1B59 was in the imaging equipment on-board the OV-1C Mohawk, a US Army observation aircraft. The OV-1C was equipped with a UAS-4 infrared surveillance system, which used a 1B59 to paint infrared reconnaissance data onto strips of film.

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The SS-501 is a large, argon-filled gas discharge tube, originally intended for use as a flash tube in offshore marine buoys. Much like the xenon flash tubes used in modern consumer equipment, this device was intended to be triggered with an external loop of wire. This tube is much larger than a modern xenon flash tube however, and requires approximately 1500 volts for operation. According to the reference guide Tube Lore, the SS501 is a "control tube", a rather vague description that leads credence to the rumor that these devices also saw use as a noise source for sonar jammers.

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This is an example of an older low power 'hard seal' helium neon laser tube. Unlike early 'soft seal' helium-neon lasers, this tube has its mirrors permanently fused to the glass envelope, which prevents the helium from escaping over time. A hard seal tube can be expected to hold its gas for several decades, as opposed to the one- to three-year lifespan of the average soft seal tube. The exact power output of this unit is unknown, but is probably at or below 1mW.

An example of a late era Uniphase helium-neon laser tube. This type of tube is relatively common and was almost exclusively used as a laser projector for early moving mirror barcode scanners. The power level of this tube is unknown, but red helium-neon tubes of this size typically output between 1mw and 2mw.

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The Sylvania C2 is a 2 watt arc lamp manufactured in a compact flat-top envelope. With a face diameter of 1 inch and a total length of 2.25 inches, this arc lamp is quite small, and is dwarfed by most other devices of its type. Although not much is known about this device, the C2 is likely a zirconia-based lamp, which contains a cathode made from a slender length of zirconium oxide. A tiny bead of zirconium on the end of the rod serves as the active element. Some variants of this tube are marked with the part number C2/DC/S, while others only carry print for the C2 prefix. Sockets for these can be difficult to find, although some Honeywell Purple Peeper flame sensors make use of the same 3 pin base, and as such can be 'harvested' for a compatible socket if no other option is available.

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This unusual device is a deteurium arc lamp, a type of laboratory UV light source. This lamp is approximately the size of a standard octal tube, but has only three leads which are covered in thick insulation. There are two rectangular chambers in the center of the lamp, with small slits in the front. There appears to be a large heater coil in the outer chamber, which is open on both ends. The lamp has an argon-like ionization glow.

Special thanks to Giorgio Basile for identifying this device.