A kicksorter or multi-channel analyser is used to produce a histogram of the heights of electrical pulses supplied to it. In nuclear physics it may, for example, be connected to a CsI scintillation counter to provide a spectrum of the gamma rays emerging from a radioactive source. The first such instruments were developed by G.W. Hutchinson and G.G. Scarrott at the Cavendish Laboratory in Cambridge around 1950. Subsequently Hutchinson moved to Birmingham and this version was built and used there. An essential feature of such a device is a memory. Here it takes the form of a series ultrasonic pulses propagated along a coil of nickel wire, mounted under the chassis and shown in image b. The histogram is displayed on the cathode ray tube. There were 60 to 120 channels with the numbers of pulses displayed vertically as binary numbers. Such homemade instruments were soon replaced by commercial versions and later completely superseded by computer-based systems.