Stránka:roll 1917.djvu/159

Things to Know and Do :27 least five words per minute before you can obtain a Govern- ment license. The Receiving Apparatus A wireless receiver is easily made, that is all except the head telephone receiver, or you can buy the whole receiving apparatus ready made. Many boys have only receiving stations, for a license is not required to listen in and wherever you live you are The International Morse Code A B c_ D E F 0' -000 -o_o -oo o 00-. a n ' l s - K --O 0.00 00 O--- -0- L M N 0 P 0-00 -- -. --- O--O . 0 R s ‘I' u --0- 0-0 000 - 0'.- V w x Y 000- O-- -OO- -0-- Z mu um 000'! um. --00 0-00. 000-. -9 000-. I Period r Idem m 00 00 O o‘o--OO --OO-- I 2 _ 3 .---- OO--- 0.0-- 4 5 6 7 0.00- .0... -.O.. .-..O 8 9 0 _---O. ----O -‘---’ cu m or - -.-0- 0-0-0,' almost sure to be within signaling range of some other station. A receiver consists of (r) a crystal detector, (2) a tuning coil, (3) a variable condenser, and (4) a pair of head telephone receivers. A CRYSTAL DETECTOR. A crystal detector in its simplest form is merely phosphor-bronze, or a German silver, point ressmg gently on a crystal of silicon or of iron pyrites. A meta frame-