英语翻译Students may begin their study of communications technol

英语翻译
Students may begin their study of communications technology by reading about some early devices and their inventors.Radios and telegraphs are part of early communications technology history,and Samuel Morse,Guglielmo Marconi,Lee DeForest,Philo Farnsworth,and David Sarnoff were communications pioneers.The first popular radios were called crystal radios because they used crystals to receive the broadcast signals.Building a crystal radio,either from a kit or from parts,is an engaging,hands-on science activity.In addition to building the crystal radio,earth science and chemistry teachers might consider making the galena crystals that receive the signals.Many early crystal radio listeners made their own galena crystals before radios were sold in stores.Teachers can also use radio assembly projects to help students learn about electricity,wave energy,the electromagnetic spectrum,the earth's atmosphere,and the sun's effects on the earth's atmosphere.Many popular electronics stores have a full range of reasonably priced,easy to assemble electronics and radio kits.