Abstract: A self-propelled apparatus for extruding and forming a substantially U-shaped concrete lining within a previously dug ditch and including means for accurately controlling the slope or grade of the interior bottom surface of the lining. The apparatus includes a hopper (41) for receiving concrete material and the lower end of the hopper is positioned within the ditch (10) and provided with an open rear end. A forming member (50) is supported for vertical movement at the open rear end of the hopper (41) and the forming member (50) with the sides and bottom of the ditch (10) together define an extrusion opening through which the concrete material passes. Control means (76) is associated with the forming member (50) for vertically adjusting the forming member (50) relative to the hopper (41) so that the slope, grade, or fall of the interior bottom wall (14) of the concrete lining is accurately controlled.

Abstract: Combined intrusion detection and fire detection, or hazard detections, alarm system incorporating, for example, a plurality of intrusion, or first hazard, detection loop circuits and a plurality of fire, or second hazard, detection loop circuits, all of controlled resistance, operatively associated to a regulated voltage source. Integrated circuit operational amplifiers are operatively associated, or connected, with said detection loop circuits, or protective loops, as comparators to compare the voltage drop across said protective loops with reference voltages to provide sensing of variation in the voltage drop across the respective protective loop corresponding to a short or an open circuit condition having developed in the respective loop by detecting variance of the respective protective loop voltage drop relative to said reference voltages so that open and closed circuit detector devices may be and are connected within the same protective loop and mixed therein.