Abstract: Apparatus suitable for use with an operative system for monitoring the operational state of at least one system component such as a valve, which can adopt three possible states. The apparatus includes a state signal generator for operative association with the component and is responsive to the state of the component. The apparatus generates a first steady state signal whenever the component is in first state, a second steady state signal when the component is in a second state and a time varying signal such as a square wave when the component is in a third state.

Abstract: A gating circuit for gating a minimum duration input signal on one of a plurality of input lines (10) to a respective output line (16). The input lines (10) are coupled to a latch (15) comprising flip-flops and the latch is enabled when a signal is applied to a clock input (18). The input lines (10) are coupled to a verifier circuit (25) which includes a verifier gate (27) receiving direct and delayed signals from a NAND gate (32) connected to the input lines (10). The verifier gate (27) applies a signal to the clock input (18) when both inputs (28,29) are simultaneously receiving a signal so that signals less than the minimum duration do not result in a signal at clock input (18). The NAND gate (41) applies a signal to locking gate (44) when any one output (16) of latch (15) is energised, and the output (47) of locking gate (44) holds a disabling signal on clock input (18) so that only the first input signal on a line (10) will be latched.

Abstract: Workpiece loading, particularly for dynamic testing of aircraft wings, is described. A double ended servo jack is drivably coupled to an upper drive lever which is pivotally mounted for movement relative to the workpiece. The follower end of the upper drive lever is coupled by a tension strap to a lower drive lever. The drive ends of the upper and lower levers are coupled to contour boards provided around the wing by means of whiffle trees so that the single jack applied both upwards and downwards forces to the wing.