A system and method for overlaying signals comprises an incumbent system, an overlay system, and a multi-access controller. The binder-fibre flocs may be held together with relatively long inorganic fibres. The plastic gear teeth may have width dimensions larger than the metal gear teeth. The sand level sensor also may be an ultrasonic transducer transmitting ultrasonic energy bursts vertically down through the water filter to the sand level and determining a time difference between a transmitted and a reflected signal. A cushion exhibiting such low seam usage and fabric usage factors and also comprising an integrated looped pocket for the disposition of an inflator can is also provided as well as an overall vehicle restraint system comprising the inventive airbag cushion. The control device is provided with a first hydraulic pump 3 for engine drive, a second hydraulic pump 56 that is driven by an electric motor 55 for pump drive, and a forwardsreverse clutch control valve 73 that performs changeover control of supply of working hydraulic pressure to the forwards clutch 14 etc.