Abstract: A distance measuring system is described which may be used as an altimeter for a helicopter or for a load carried by its winch. The system comprises: a transmitting transducer for converting a first modulated electrical signal into a corresponding acoustic signal to be directed towards and reflected by a surface; a receiving transducer for converting the received reflected acoustic signal into a corresponding second electrical signal; and a correlation processor for receiving the second electrical signal, or the first and second electrical signals, and correlating the modulations thereof to produce an indication of a time delay thereof from which the distance travelled by the acoustic signal can be determined.

Abstract: A distance measuring system is described which may be used as an altimeter for a helicopter or for a load carried by its winch. The system comprises: a transmitting transducer for converting a first modulated electrical signal into a corresponding acoustic signal to be directed towards and reflected by a surface; a receiving transducer for converting the received reflected acoustic signal into a corresponding second electrical signal; and a correlation processor for receiving the second electrical signal, or the first and second electrical signals, and correlating the modulations thereof to produce an indication of a time delay thereof from which the distance travelled by the acoustic signal can be determined.

Abstract: An apparatus for dislodging or loosening mucus in a person's lungs, for example of a sufferer of cystic fibrosis, comprises a bath arranged to receive the person and filled with water such that the person's chest is immersed in the water. A vibrator vibrates the liquid so that the vibrations are transmitted to the person's lungs. In use the vibrations are preferably at the pulmonary resonant frequency or Helmholtz resonant frequency of the person's lungs.