The present invention is directed to a method and apparatus for providing variable output drive capability to an output driver. The security device includes an optically variable structure for controlling emission of luminescent radiation of at least one of the first and second wavelengths from the security device, the security device being arranged to permit, from an area of the optically variable structure, emission of luminescence of the first and second wavelengths from the security device. The lower member may have a first side and a second side.