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thc numerals from 0 to 9. The cathodes aro arrangcd so that one falls under cach porforation. When sufTiciont volt-age to ionize the gas is applied between the disc anodo and ono of tho cathodes. tho rosulting ionization glow is visible through tho corrosponding numerical porforation. In Fig. 2. tho cathodo under number 5 is activatcd. Numerals can be illuminated in succossion as tho voltago applied is shiftod from cathodo to cathodo.

The Nixie is also a gas-filled tubo containing ton cold cathodes and a common anodo. In this case, however. tho cathodes thomsolvos aro shapcd liko tho numerals from 0 to 9. Whcn sufTiciont voltagc is applied botwoon tho anodo and ono of tho cathodes. tho ionization glow surrounding tho selected, numeral-shaped cathodo pro-vides visual roadout. To accommodate difforont applications, Nixio indicators aro available in a varioty of sizos rang-ing from tho miniaturo to jumbos that provide roadablo indications 150 foct away. Throo sizos aro shown in Fig. 4. Tho numoral 5 above oach indicatos tho rolativo sizo of indications, which are viewod looking down at tho tubos whon thoy aro in tho positions shown.

Fig. 5 shows two comploto, compact, decado counters. Tho ono on tho loft in-cludos an intogral Nixie indicator, with tho latter horizontally mountod to pro-vido oasy. hoad-on roading. A numbor of thoso compact decadcs can bo con-noctod in cascado and mountod so that thoir Nixies provide in-lino roadout. Tho countor at tho right is a similar unit that is usod to control a remotely located Nixie.

The Glow-Transfer Tubę

Ono type of multi-electrode tubo has boen dosignod so that it can bo oper-atcd as a complote, self-indicating decado countor. with no external roadout devicc roquired. Like othor indicator tubos. it is gas-filled. has ton cold cathodes. and a single anodo. However

Fig. 2. One of 10 cathodes in Pixie glow* through peHoration in the anodę.

it also has othor olomonts to make tho counting function possible. which will bo discussed shortly, and tho cathodes aro pin-likc structures arrangcd in a circlo around tho disc-shapod anodo. Whon ionization occurs botwoon tho anodo and one of the cathodes, tho glow appoars as a bright, visible spot at tho tip of thc cathodo pin. As input pulsos aro applied to tho tubo. ionization transfers around the circlo from cathodo to cathodo. with tho position of tho glow thus providing an indica-tion of the pulsc count.

A countor. mado by Went port Electric. using glow-transfer tubos is shown in Fig. 7. Tho ton cathodo positions for oach tubo havo becn n urn be red cx-ternally. so that tho position of tho glow can bo road as a docimal digit on oach tubo. Aftor ton input pulsos have boon applied to a glow-transfer tubę, tho glow roturns to tho initial cathodo and tho tubo produces an out-put pulso. as do othor decado counters. This output may thon be usod to trig-gor another tubo of tho samo typo to indicato tho next decimal position. Tho countor of Fig. 7 usos five glow-trans-fer tubos in cascado. ft thoroforo has

a total counting capacity of 10*. or

100.000.

Concerning tho tubę itself, for each cathodo thoro aro two additional elec-trodes. callod guide pins (soe Fig. 8). The cathodes are laboled K₀ through K*. Between any two adjacont cathodes. there is a pair of guide pins (Gi and G: for oach pair). Tho lattor serve to transfer tho glow from ono cathodo to tho next. Ali of the guide pins iden-tified as G, aro tiod togothor internally and brought out to a single pin on the base of the tubo. Ali G_s guide pins aro similarly tiod togothor internally and brought out to a single connoction on tho tubo base.

Whon voltage is applied to tho glow-transfer tubo. ionization occurs botwoon the anodo and ono of tho cathodes. Thoro is an external anodo resis-tor. shown in Fig. 6. across which a voltagc drop occurs whon tho tubo has startod to conduct hetween any ono cathodo and tho common anodo. This drop immcdiately lowers voltage across tho tubo so that it falls bolow tho firing point. Thus a glow cannot form at any cathodo except tho ono that has al-ready boon ionizod. and only ono cathodo at a timo can bo activated.

In order to transfer tho ionization glow from ono cathodo to tho next adjacont ono, we must apply two nega-tive pulsos to tho tubo. ono to tho G_t pins and tho othor to tho G- pins. Furthermorc. as shown in Fig. 6. those pulsos must overlap in timo. so that all G, pins become negative boforo tho G_a pins do. but that tho G- pins romain negative for a short timo aftor tho G, pulso is complotod. Thoso requircments would soom to complicato practical appliention of tho glow-transfer tubo, but tho mat tor can bo resolved simply: a single pulso sourco may bo usod. with a dolay network foeding to tho G_a Circuit.

Whon any particular cathode in this tubę is glowing. this is because it is tho most negative elcctrode in its group

Fig. 3. (Upper leli) An application oi in-line readoul: a digital voltmeter Ihal provides guick. direcl readings.

Fig. 4. (Above) These 3 Nixie sizes. from leli to right are super, standard, and miniaturę. Digits at top show reiatlve size oi indications. seen looking down at tubes.

Fig. 5. (Lower leit) Burroughs decade counters in^luding Nixies. like one at lelt. mount side by-side lor in-lino readout. Decade at right Controls remotely located Nixie.

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ELECTRONICS WORLD