Abstract: An anti-locking control system is described in which the by electrical interference in the range of the mains frequency of conventional power supplies are detected and eliminated. To that end, in the range of critical speeds, a new reference vehicle speed is formed from the ascertained vehicle speed only if the time intervals between the arriving signal edges of the various rpm sensors are not in the range of the mains frequency.

Abstract: To provide an indication of the presence of a trailer connected to a vehicle, operating as a tractor, without any additional terminal or contact elements on a plug-socket connector between the electrical system of the tractor and the trailer connected thereto, a logic gate (11), preferably a NAND-element, is connected to the output line of the direction flasher circuit, or other suitable connecting line, to a low-resistance load on the trailer, for example the brake light (19a), position lights or the like, the resistance circuit element including a connection from the positive power supply through a resistor (12) having a value which is high with respect to that of the lamps on the trailer (19, 19a) so that, with the trailer disconnected, an effectively 1-signal will be applied to the logic circuit but, upon connection of a low-resistance lamp, that is, upon connection of a trailer socket, the signal at the logic gate will drop to a O-signal although the current through the lamp is insufficient to cause ligh