Abstract: An early warning signal is produced when there is a danger of ice forming on a road surface by means of a device comprising a temperature sensor for determining the ambient temperature, a sensor unit for determining the temperature and moisture of the road surface, a heatable sensor unit having a heating element and a moisture-detecting gap, and comparators for comparing the voltages supplied by the temperature sensors and the moisture sensors with reference voltages, comprises in addition thereto a sensor unit having a further moisture-detection gap, one or more elements for alternately cooling or heating this further moisture-detection gap, and a temperature sensor for determining the temperature of this further moisture-detection gap, as well as signal generators generating signals in response to the output signals of the comparators for indicating whether the road surface is dry, wet, or icy.

Abstract: Automatic valve for controlling the passage of an in-feed pressure fluid to be delivered in predetermined quantities into one receiver. After delivery of the predetermined quantity, the flow to the one receiver is cut off and the flow is directed to the next receiver. The receivers may be sequential nozzles of a sprinkler system. The automatic control valve comprises two tandem-joined piston cylinders. The first piston cylinder comprises two cavities of different volumes. The second piston cylinder comprises only one cavity. There is placed a piston in each of the cavities of the first piston cylinder, which pistons have different diameters and the circumferential surfaces spaced from the inside walls defining the respective cavities of the first piston cylinder to afford flow of pressure fluid past the pistons. The cavity of the second piston cylinder comprises a shock-absorbing device, or dash pot connected with a common piston rod carrying also both the pistons in the cavities of the first piston cylinder.