Here in SA we say "double Transmition" instread of Blocked. I think its important to be told if there has been a double tx so that no info is lost or misunderstood. We have a side tone on our Headsets which means that we hear the Tx as we make it and if someone blocks us whilst we tx we hear that annoying whining and whistling that goes with a double tx and generally release the foot switch and wait for the idiot that wasn't listining to get off the freq.
Personally my pet hate is when an acft is handed over from one sector to the next and they just hit the comms button and start Tx with out listening 1st. Bad radio etequite (Can't spell).
Having not heard of contran till this forum I used the link above to see whats it was about. I think the best feature is the stuck PTT problem quote
"The secondary function of CONTRAN® alerts the flight crew to an onboard unintentional transmission or ‘stuck-microphone’. If the fault cannot be rectified then automatic termination of the transmission follows."
This I think is great as almost daily some idiot sits on his Ptt and we hear all about his meal etc nothing worse than trying to get acft to miss when you can't speak to them cause all they hear is WOOOOOPPP
About using Blocked It is shorter than Double transmition so I think I will try it out