<simpleType name="receiverTypeEnumType">
  <annotation>
    <documentation>1) accelerometer: an instrument for measuring acceleration of the earth. 2) electrode: a device set up (typically a pair of metal rods with a voltmeter connecting the two) for measuring the electrical potential difference in the earth between the electrode pair. 3) Geiger-Muller counter: a device for measuring radioactivity by detecting and counting ionizing particles. 4) geophone: a device that measures velocity by converting ground movement into voltage. 5)gravimeter: an instrument used to measure gravitational acceleration. 6) hydrophone: a microphone designed to be used underwater for recording or listening to underwater sound. 7) magnetometer: an instrument for measuring the strength and direction of magnetic fields, 8) RF coil: a receiver of radiofrequency signals in equipment used in magnetic resonance and electromagnetic induction methods. 9) radio wave antenna: an antenna attached to a receiver used to detect radio waves (a type of electromagnetic radiation with frequencies of 300 gigahertz (GHz) and below). 10) scintillation detector: an instrument for detecting and measuring ionizing radiation by using the excitation effect of incident radiation on a scintillating material, and detecting the resultant light pulses. 11) seismometer: an instrument used to measure ground motions by detecting relative movement between a "stationary" mass and a frame coupled to the earth. Typically seismometers contain sensors to measure motions on multiple axes. 12) sodium iodide detector: a device for measuring gammma radiation at various frequencies that uses sodium iodide as the detector. 13) VLF receiver antenna: an antenna designed to detect radio frequencies in the range of 3-30 kHz.</documentation>
  </annotation>
  <restriction base="string">
    <enumeration value="accelerometer">
      <annotation>
        <documentation>accelerometer - accelerometer value.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="electrode">
      <annotation>
        <documentation>electrode - electrode value.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="Geiger-Muller counter">
      <annotation>
        <documentation>Geiger-Muller counter - geiger muller counter value.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="geophone">
      <annotation>
        <documentation>geophone - geophone value.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="gravimeter">
      <annotation>
        <documentation>gravimeter - gravimeter value.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="hydrophone">
      <annotation>
        <documentation>hydrophone - hydrophone value.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="magnetometer">
      <annotation>
        <documentation>magnetometer - magnetometer value.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="RF coil">
      <annotation>
        <documentation>RF coil - rf coil value.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="radio wave antenna">
      <annotation>
        <documentation>radio wave antenna - radio wave antenna value.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="scintillation detector">
      <annotation>
        <documentation>scintillation detector - scintillation detector value.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="seismometer">
      <annotation>
        <documentation>seismometer - seismometer value.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="sodium iodide detector">
      <annotation>
        <documentation>sodium iodide detector - sodium iodide detector value.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="VLF receiver antenna">
      <annotation>
        <documentation>VLF receiver antenna - vlf receiver antenna value.</documentation>
      </annotation>
    </enumeration>
  </restriction>
</simpleType>