Memory devices for storing the peak, instantaneous or integral values of the variable input

986, 757. Electric selective signalling systems. LIGNES TELEGRAPHIQUES ET TELEPHONIQUES. Oct. 23, 1962 [Nov. 8, 1961; Oct. 1, 1962], No. 40065/62. Heading G4H. In a gas chromatography system the position of a recording pen 0, Fig. 1, is converted into a corresponding amplitude significant voltage which signal is then converted into a frequency significant pulse train, by a frequency modulator, demodulator and shaper 2, 3, 4, the pulses of which are then counted 5 so as to produce a count representing the integral of the input displacement with respect to time. The contents of the counter 5 are transferred to relay stores 8 1 to 8p via a switching arrangement 6, 7, at appropriate times, so that each store records data relating to a single gas constituent. The outputs from the stores may be used for any purpose for example in a computer 12 for computing the calorific value of the gas mixture being analysed. In a modification (Figs. 2 and 4 not shown) a capacitor is charged to a level corresponding to the maximum displacement of the pen which charge is then digitised and stored by integrating, with the circuit shown in Fig. 1, the voltage across the capacitor as it discharges through a known resistor.