The invention relates to a liquid-crystalline medium based on a mixture of polar compounds of positive dielectric anisotropy, characterised in that it comprises one or more ester compounds of the formula I 1and one or more compounds of the formula IA 2in which R1, R2, ring A, ring B. The method is comprised of the following steps: pressing a presser against the passenger seat; detecting output signal levels of the sensing cells; and. Access to the shopkeeper’s management space is controlled by authorized list. The delay elements can be capacitors.