Abstract: Display apparatus receives from a transducer a voltage analogue signal representing the parameter to be measured and uses the signal to produce an illuminated band-representation of the parameter by a series of semiconductor light emission devices. A zero value of the analogue signal is represented by a band terminating intermediate the ends of the series so that positive and negative analogue values are measured, and it is indicated, for example by flashing the illuminated band on and off, when the analogue value exceeds predetermined positive and negative tolerance limits which are both within the measuring range of the apparatus, the indication being such as to draw an operator's attention to the displayed out-of tolerance value.