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: An anti-block control system has four identically designed control channels. Safety circuits (8, 8') are also provided for monitoring the system, as are devices for testing the operability of the system. In this test, performed while the vehicle is stopped or when it is started, a test signal is fed into the channels and the effects of this signal are compared, in pairs, at locations of the controller corresponding to one another. A signal train is formed when the comparison is made. In accordance with the invention, two safety circuits (8, 8') are provided, each associated with a pair of channels, and the signals from all the channels are supplied, in pairs, to the safety circuits. The safety circuits include timing elements. During a test cycle, the signal trains in the two channel pairs generated by using the test signal are compared with one another by use of two comparator circuits (23, 23'), and in the case of non-agreement, a warning or switching signal (18, 18', 31) is generated.

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