GB996761A - Improvements in or relating to pushbutton devices - Google Patents

Abstract

996, 761. Photo-electric control devices. EXPRESS LIFT CO. Ltd. May 22, 1963 [June 29, 1962], No.25101/62. Heading G1A. [Also in Division H3] A device comprises a light source 2 Fig. 1, a photo-electric sensor 1, a shutter 7 movable between positions in which it shields and does not shield the sensor from the light source, a pushbutton 4 mechanically connected to the shutter, and a translucent shield 6, the light source being operable at two intensities of illumination the higher of which is effective to illuminate the pushbutton through the translucent shield. In the embodiment sensor 1 is a photo-transistor and two filament lamps 2 constitute the light source. In the circuit arrangement, Fig. 2, the collector of the photo-transistor is connected to a NOR unit 13 the output from which is connected to a NOR unit 15, having a second input 17; thus units 13 and 15 connected as shown afford a memory circuit which is reset by a signal 17. Output 18 is fed to a NOR unit 21 the output from which controls lamps 2. NOR unit 21 Fig. 3 includes a transistor 25 the base of which is connected to inputs 20 Fig. 2; its output circuit is connected in parallel with a resistor 26. When transistor 25 is non-conducting i.e. in the present convention when there is a '1' output from NOR unit 21, lamps 2 glow at low intensity sufficient to excite photo-transistor 1 but, because of shield 6 Fig. 1, insufficient to illuminate push button 4; when transistor 25 is conducting, lamps 2 glow sufficiently to be seen from in front of the push button. In operation, assuming that the latest event is a reset i.e. '1', input to NOR unit 15 there is a 'O' output from the latter and thus lamps 2 glow at low intensity and phototransistor 1 produces a "O" output. If the push button is now pressed momentarily, there is a "1" output from the photo-transistor and the lamps 2 glow at high intensity. The push button may be utilized as a landing call button in a lift service, the higher illumination indicating to the caller that the call has been registered; when the call is answered a reset signal is applied at input 17.