Abstract: Operation between a beam switch which directs light to a photoelectric detector and a gating means for directing signals from the photoelectric detector to separate storage channels is synchronized by generating a marker pulse within a sequence of clock pulses which correspond to the positions of the beam switch. Signals from the separate storage channels are directed to an analyzing means in a predetermined sequence by the gating means and sequencing within the analyzing means is also accomplished thereby. Furthermore, comparative analysis between signals corresponding with two positions of the beam switch is provided at the input to and/or the output from the separate storage channels.