In a two-stage inverter circuit including an inverter circuit constituted by first and second FETs and an inverter circuit constituted by two FETs, a source and a gate of a third FET are connected to a first power source and a second power source, respectively. With the actuator being less than fully extended, the stop mechanism and actuator can exert opposing forces that help prevent the deck from rocking back and forth as the deck settles to its stationary, upright position. Two or more magnetic field sensing elements, which are often stationary, measure the directionality of the resultant magnetic field at different positions for a particular angular shaft position. ; n represents 0 or 1; and a to c represent such numbers that the polymerizable compound has at least one or more of any of X, Y, and Z). In the second embodiment the tray is fitted with a fixed upstanding rib member rather than one which may be folded away. The method is particularly effective in measuring changes in cyclic adenosine 3,5-monophosphate coupled to cell receptors in insects.