1,024,796. Coating apparatus. METAL BOX CO. Ltd. Sept. 14, 1964 [Sept. 25, 1963], No. 37769/63. Heading B2B. [Also in Division G1] In apparatus for applying material to an area of an article and to detect any discontinuity in the material applied, the articles e.g. carton blanks are moved in succession by endless belts 2 past an adhesive applicator wheel 3 against which a carton flap is pressed by spring-loaded wheel 6. The blank is subsequently passed through apparatus for forming it into a carton. The adhesive coated areas are scanned by photo electric means comprising basically of lamp 20 and a photo multiplier 11 (Fig. 4) which is electrically connected via line 12 with a fault registering device 13. The latter is controlled by the sensing of leading and trailing edges of a blank by photo-electric cell 23 via line 26 so that the fault-registering device 13 is conditioned to receive fault-indicating signals whilst the blank is interposed between light 24 and cell 23 and when the trailing edge passes cell 23 the device 13 transmits an actuating signal along line 27 to fault indicating device 28 if a fault has been sensed. The device 13 may pass corresponding signals to audible and visual fault indicating devices 31 and 32. The fault indicating device 28 comprises an electronic shift register consisting of register units 34 connected in series. A driver circuit 35 is connected to unit 28 by line 36 and is arranged to produce a succession of shift pulses to transfer an actuating signal in succession from one unit 34 to the next. The driver circuit 35 is operated in synchronism with conveyer 7 which is transmitting the blanks received from the adhesive application device by means of disc device 38 in conjunction with lamp 41 and equi-spaced radial light reflecting elements 39 and photoelectric cell 42. The arrangement is such that when a fault indicating signal has been entered on the shift register 28 and reaches the last unit thereof the blank has travelled a definite predetermined distance along the machine and is positioned before a solenoid operated pulse element controlled from the switching means 44 and the actuating device 46 such that a carton which has been found to be faulty by the photomultiplier 11 is displaced from the line of carton blanks. The photo-multiplier 11 detects faults in the coating applied and also the absence of blanks.