However , there was some resistance among the Marconi operators about adopting the new signal , and , as late as the April , 1912 sinking of the RMS Titanic , the ship 's Marconi operators intermixed CQD and SOS distress calls . However , there was some resistance among the Marconi operators to the adoption of the new signal , and , as late as the April , 1912 sinking of the , the ship 's Marconi operators intermixed CQD and SOS distress calls .