has itself branched into an even greater number of subcategories,such as radio frequency(RF)systems,telecommunications,remote sensing.signal processing,digital circuits,microelectronics,instrumentation,audio,video and optoelectronics. s The field of electronics was born with the invention of the thermionic valve diode vacuum tube in 1904 by John Ambrose Fleming.The vacuum tube basically acts as a current amplifier by outputting a multiple of its input current It was the foundation of all electronics,including radios,television and radar, until the mid-20th century.It was largely supplanted by the transistor,which was developed in 1947 at AT&T's Bell Laboratories by William Shockley,John Bardeen and Walter Brattain,for which they received the 1956 Nobel Prize in physics. 4电气工程英语