he knew more than how to replace a tube - he knew the laws of electro-magnetism , knew why the angels of the unseen energy danced the way they did , knew the reason and rules they used to flow through diodes , to wait and discharge their capacitance , to oscillate at this sine curve or that , to merge then part then orchestrate them come together fired from an electron gun 1000 directions at once ( or to you , it seemed at once ) to make a face on a cathode tube or vibrate the carbon paper stretched across a magnet to bring you to the edge of your chair straining to hear the outcome of a voice spinning tales of mystery or murder or romance .