ABOVE IS THE MARCONI MARINE 'MERCURY' RECEIVER - WHICH WAS A LF TO 4MHZ RECEIVER - ON A DEEP-SEA VESSEL THIS RECEIVER WOULD BE ACCOMPANIED BY THE 'ELECTRA' RECEIVER WHICH HAD EXTENDED FREQUENCY COVERAGE TO ABOUT 25/30 MHz. QUITE A FEW OF SHAW SAVILL'S VESSELS  HAD THESE RECEIVERS AS THE MAIN RECEIVER SET UP - INCLUDING 'MV CANOPIC' AND MV 'CEDRIC' .