THE WORLD'S ADVANCE for JULY 



129 



" 325 Page Electrical 

 s 'and Wireless Catalog 



Is a TREATISE on ELECTRICITY and WIRELESS. With prices a little M 

 lower than the lowest. Bound in imitation leatherette with bronze lettering. 



This unrivalled catalog mailed to anyone upon receipt of 8c in stamps or coin which may be 

 deducted on first dollar purchase. Great cost of catalog arid low prices prohibit distribution otherwise. 



WHY WASTE TIME AND POSTAGE IN SENDING FOR A DOZEN CATALOGS 



when this catalog contains practically everything worth while in wireless 

 and electrical goods, advertised in this and all other magazines, and in 

 most cases at more attractive prices. 



'18 



IMPROVED TYPE RJ4 



AUDION DETECTOR 

 5 Contact Points-Finer Adjust- 

 ment-- More Sen si live Than Ever 



The Audion Detector is 1% to 3 

 times as sensitive as any form of 

 crystal or electrolytic detector. 

 These two characteristic testimo- 

 nials from Council Bluffs. la., and 

 St. John, Kans.. speaks for themselves. 



"I suppose it sounds almost unbeliev- 

 able when I say that I can hear Port 

 Arthur (VBA) with the phones a foot 

 away from my ears and (NAR) Key West 

 almost that far, but such is the fact." 



125 pp. Wireless Apparatus for 

 Commercial and Experi- 

 mental use; 

 10 pp. Raw Material ; 

 5 pp. Transformers ; 

 8 pp. Storage Batteries ; 

 15 pp. Telegraph Insts. ; 

 42 pp. Motors and Dynamos; 

 10 pp. Miniature Lamps ; 



What This Big Catalog Contains 



8 pp. Flashlights ; 

 5 pp. Massage Vibrators ; 

 10 pp. Miniature Railways; 

 5 pp. Lighting Plants ; 

 10 pp. Ammeters and Volt- 

 meters ; 



25 pp. Electrical and Me- 

 chanical Books ; 



2 pp. Fans ; 



12 pp. Telephone Equipment; 

 6 pp. Heating Appliances; 



10 pp. Auto Accessories ; 



13 pp. Victrolas, on our Easy 

 Payment Purchase Plan; 



(No Down Payment;) 

 30 pp. G e n e r a 1 Electrical 

 Supplies. 



SEND 8c for THIS CATALOG TODAY 



(Reasons for requesting 8c mentioned above) 



The most elaborate, comprehensive, educational and artistic catalog in its line published. 

 Glance through the contents. Note the amazingly low prices of products representative of the 

 best in the field of electrics. Then you will know why the overwhelming mass of users of electrical 

 and wireless supplies have for so many years adopted the slogan: 



"IF DUCK SELLS IT, IT MUST BE GOOD; 

 IF DUCK DOES NOT SELL IT, THERE'S A REASON" 



THE WM. B. DUCK COMPANY 



432-434 

 St. Clair Street, 



TOLEDO, OHIO 



Halcun Wireless Apparatus 



INCLUDES 



Rotating Gaps Tuning and Loading Coils 



Sending Condensers Variable Condensers 



Leakage Transformers Fixed Condenser 



Oscilation Transformers Loose Coupler 



Aerial Switches Wavemeters Detectors 



COMPLETE SENDING and RECEIVING SETS 



Priced Right Shipped Promptly 



Made Well 



SEND STAMP FOR DESCRIPTIVE CATALOGUE 



HALLER-CUNNINGHAM ELECTRIC CO., San Francisco, Cal. 



THE DE FOREST AUDION DETECTOR 



INCOMPARABLY SUPERIOR TO 



Type RJ4 $18.00 



ANY OTHER KNOWN TYPE" 



. (Not Injured by Static) 



The United States Bureau of Standards 



states that it is fully 50 per cent, more sensi- 

 tive than any other form of detector. No 

 better authority could be quoted. 



Send 4 cents in stamps for 1 6-page com- 

 plete bulletin. 



DE FOREST RADIO TELEPHONE & TELEGRAPH CO. 



101 Park Ave. New York, N. Y. 



For our Mutual Advantage mention The World's Advance when writing to Advertisers. 



