Safety contact elements are permanently monitored and evaluated by safety switch devices. On moving systems such as automatic sliding gates, the electric signal has to be transmitted by the mobile safety contact edge on the door leaf. In order to guarantee this transmission, different signal transmitting systems with ISK/OSK safety switch devices can be used. These systems are contact-free, making ASO signal transmission systems abrasion-proof. They have been tested and certified according to the guidelines of the latest European standards.