"Transducer down" should be the orientation of the receiver/transceiver if it is topside, or the orientation of the transmitter/transponder if it is topside.
"S" package Mk III Transceiver in "transducer down" orientation
"S" package Mk III Transponder or Mk II transmitter or Mk II receiver in "transducer down" orientation
"P" package Mk III Transceiver in "transducer down" orientation
"P" package Mk III Transponder or Mk II transmitter or Mk II receiver in "transducer down" orientation
