Abstract: The present invention is directed to a circuit incorporating a pressure-sensitive switch that operates in a normally-open position and disables an associated survey sensor (e.g. a hydrophone) at predetermined depths. The circuit comprises a non-mechanical switch connected in series with the sensor and also connected to the pressure-sensitive switch so that when the pressure-sensitive switch is closed, the non-mechanical switch becomes non-conductive relative to the associated sensor, thus causing the signal from the associated sensor to be disconnected. The circuit may be connected with an associated sensor in parallel with an array of other sensors so that the circuit does not affect the operation of the other sensors in the array.

Abstract: The leaky or non-leaky condition of a membrane-sealed container is determined by causing motion in one direction of one portion of the membrane; sensing motion in a direction opposite the first direction of another portion of the membrane; and delivering a corresponding signal indicative of the leaky or non-leaky condition.

Abstract: The leaky or non-leaky condition of a flexible, closed container is tested by increasing the pressure within the container (by causing motion of a wall of the container), and monitoring the resulting rate of change of a predetermined parameter (wall position or force exerted by the wall); the monitored rate of change indicates the leaky or non-leaky condition. In another aspect the time-varying net force on a container is the basis for determining the leaky or non-leaky condition.