Abstract: A vehicle simulating frame assembly is supported on a track recording surface by pairs of non-dirigible tractor wheels spaced laterally outward of track marking devices plotting parallel spaced track lines on the surface in response to wheeled movement of the frame assembly along a path recorded as a center guide line equally spaced between the track lines. The frame assembly is steered along the path by a dirigible guide wheel aligned with said center guide line and angularly displaceable by means of a steering spindle between angular limits corresponding to the maximum steering cramp angle of the vehicle being simulated.

Abstract: A liquid level monitoring device operable either to detect leakage from a body of liquid or to detect deviations from a controlled rate of withdrawal from a body of liquid. The device employs a pressure responsive diaphragm which, in the face of unequalized pressures applied to its opposite sides, is operable to actuate a control switch. One side of the diaphragm is exposed to a constant pressure, which may be atmospheric, while the other side of the diaphragm is connected to an open ended probe submerged in the body of liquid. When employed as a leak detector, the device is set by opening a solenoid controlled valve connected across a diaphragm to equalize pressure at opposite sides of the diaphragm while the probe is submerged in the body of liquid.