A method for driving a liquid crystal display device provides sufficient charge time for a pixel unit by adjusting a main-charge time and a precharge time of the pixel unit according to the polarities of data driving signals applied during a main-charge period and a precharge period. According to the invention, this is achieved in that a holder and a signal generator for the connection to the holder are provided, the signal generator comprising a base housing made of plastic and penetrated by at least two contact elements, and the function elements of the signal apparatus. A fastener is attached to each pants leg, either at the hem or some inches above the hem. Providing at least a first 2f modulation reference signal has advantages over the prior art, because by using such a reference modulation signal it is possible measure the absolute intensity and therefore to receive the same result at different temperatures or at mode hopping of the laser.