Oscilloscope, c 1960s.
© Science Museum / Science & Society Picture Library
An oscilloscope displays electrical waveforms. Although the waveshape of voltages was able to be viewed during the 19th century, it was not until the progres in electronics during World War II that the oscilloscope (as it was by then generally known) became what it is today. This device is commonly used for testing electric cicuits and displays the oscillating current on its screen.