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Show HOW RADIO MESSAGES ARE SENT I m Bl PB Mv GEORGE it lei ked ami ipprovcd i Radio Section, Sec-tion, i . B. Bureau of Standards i There are now more than 15,000 li-Cenaed li-Cenaed wireless sending stations in tin: United States. Of these approximately approximate-ly 13.000 are amateur stations Government Gov-ernment and commercial stutlons comprise com-prise the remainder. LICENSING REQUIRED Licensing Of both sending stations and sending bpeVatora is required bj federal law Those licenses are Issued by the i'nlted tftat'-s Department ol ommerce. The niajority of the licensed sending stations are equipped for radio telegraphy teleg-raphy only, but an increased number of them are being equipped for the IdispaUh of messages by radiophone I also. Among the large commercial radio -' phone s ndlnjr stations are those of I the Westlnghouse Electrical Com-1 Com-1 pany at Newark, Pittsburg and Chl-1 Chl-1 cago. which broadcast music and news over a combined radius of mor" than 1000 miles. Tho Washington radiophone station of the Postofflce Department covers a radius of 10a miles. Dongcr distances dis-tances are covered at nihi. t'nder favorable fav-orable conditions messages from the Washington Station hae been heard in Texas RADIO APPARATt s Of the several types of sendinv; stations in existence, the illustration shows one that has been designed by the 1". S. Bureau of Standards fori i experimental purposes The five, tubes on the instrument are electron TXPE OF RADIO FRANSlflTTEB DESIGNED BY I m I s BUREA1 !I STANDARDS. j tubes, the most important part of I the apparatus used in radio com-Imunlcation, com-Imunlcation, These tubes will be ex-I ex-I plained in a separate article, In the Illustration S phonograph la playing into the equipment direct. , T) fend out instrumental or ocal 'music rendered by Individuals a modified modi-fied telephone transmitter, shaped 'somewhat like a megaphone but cm-I cm-I bodying the same principals as contained con-tained in the ordinary telephone traps -' mltter Is used. VOICE 1 RANSMISSION When the receiving apparatus Is iconnccted. sounds of any kind are caught by the insirumont throiiBh f the telephone transmitter. The eleo- H are modulated h the g waves and the whole Is allenth H sent out into space to be caught and kH made audible by the receiving inslru- kBSBsfl The largo commercial broadcasting itlona operate on a wave length of 360 meters and have a carrying range .no to 300 miles. in amateii" transmission the wa. length la re- gskH stricted to not more than 200 meters to prevent, so far as possible tho glll confusion of messages In the same gftssV " l" SBBBBV |