Radio age (Jan-Dec 1926)

44 RADIO AGE for December, 1926 ■DESULTS authorities. A slight turn obtains correct tube oscillation on all tuned radio frequency circuits. Neutrodyne, Roberts two tube, Browning-Drake, McMurdo Silver's Knockout, etc.capacity range 1.8 to 20 micro-micro farads. Price $1.00 Model "G" With grid clips obtains the proper grid capacity on Cockaday circuits, filter and intermediate frequency tuning in heterodyne and positive grid bias in all Capacity range: Model G-l .00002 to .0001 MFD. Model G-5 ,0001 to 0005 MFD. Model G-10 .0003 to .001 MFD Price $1.50 X-L Push Po.t Push it down with your thumb, in wire, remove pressure and wire is firmly held. Releases instantly. Price 15c. Also furnished seven to a strip. Nicely marked in w with seven standard markings. Price $1.50. Information on Request X-L. RADIO LABORATORIES 2424 N. Lincoln Ave. Chicago, Centralab Radiohms. Modulators, Potentiometers or Rheostats are standard on 69 leading radio sets. Ask your dealer, or write for descriptive literature. CENTRAL RADIO LABORATORIES, 24 Keefe Ave., Milwaukee, Wis. Gen SqS Blue Prints PDITIT Write for a complete description r I\L,Ei 0f the Peer of all receivers — the World's Record Super 8, 9 and 10 the wonder receivers that hold 4 fully verified World's Records for distance. The World's Record Super is one of the few receivers to bring London into' Chicago during the last two International Contests. Thousands of testimonials hail the World's Record Super 8, 9 and 10 as the marvels of Radio. Write for free list of records and testimonials todayl Easy to Build 5fou caii build an exact duplicate of the original World's Record Super models by following our Blue Prints. Building instructions complete in every detail with each set of Blue Prints make it easy for anyone to build this remarkable receiver with perfect success. Complete Building instructions and Blue Prints $5.00. Remit with order or we will send C. O. D. Mail the Coupon Today! M-S SYNDICATE Box 2131, Cleveland, Ohio M-S SYNDICATE, Box 2131, Cleveland, Ohio □ Please send me free literature and verifica tions of the records made by the World's Record Supers. □ Am enclosing $5 for Blue Prints, etc. □ Send me Blue Prints, etc., C. O. D. NAME ADDRESS.. Design and Manufacture of Resistor Units (Continued from page 20) Second, it is comparatively easier to put a protecting layer over the conducting filament. Third, it is easier to make measurements of the conductivity of the coated fibre as the fibre is fed out of the coating machine. The case of measurement obtained in the case of the fibre insures a uniform product. After the conducting coating has left the furnace it is next coated with durable protective film of insulating varnish which is then thoroughly dried by the application of heat. This impenetrable coating completely -protects the conducting filament against atmospheric changes. As the coated glass filament passed through the various stages of manufacture, its resistance per unit length is continuously tested. Literally, there is no inch of this fibre which has not been measured for resistance. After the wire has passed through the measuring devices it is cut automatically in two foot lengths. It is then kept in sealed tubes until it is required for assembling the complete unit. Finally the wire is cut into lengths approximately 13,4" long and mounted in a glass tube with brass caps at two ends. A new form of power resistor has recently been developed by the engineers of the company. In this type of unit the filament is wound into the form of a helix, the diameter of this helix being exactly the outside diameter of the enclosing tube. The two ends of the helix are embedded in an alloy within the caps. The helix permits the use of a very long heavily coated fibre in a very small space. With this device it is possible to dissipate from two to five watts depending upon the size of the unit with less than ten per cent variation in the resistance of the unit. The alloy in which the filament is embedded in the caps, is the result of innumerable experiments. Its properties are such that it makes perfect electrical contact with the filament. The cap grips the contacting filament The Magazine of the Hour so tightly that it is impossible to pull the filament out without shattering it. It is almost as if the cap, filament and alloy were made of one piece. After the resistors are assembled they are again tested. The resistance units are normally made within a five per cent variation. On special orders it is quite possible to make them within two and one half per cent. All the meters used in the manufacture and assembly tests are constantly checked against laboratory standards. 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Booklet of valuable information and form for properly disclosing your idea free on request. Write today. RICHARD B. OWEN, Patent Lawyer 81 Owen Bldg., Washington, D. C. 41-M Park Row, N. Y. City Please Mention Radio Age When Writing To Advertieers.