Tracking vessels at sea

After reading The Times (July 23), I checked the internet on the use of VMS (vessel monitoring system) as I assume this was fitted to the ill-fated Simshar.

It seems that, in many parts of the world, this satellite-based system has to operate at all times and is strictly monitored every one to two hours. The VMS uses battery power when the boat engine is not running, not, as Anthony Gruppetta argues, only when the engine is running, unless this is a concession in Malta.

I am unsure whether any of the fishing boats use the free-floating marine ELT (emergency locator transmitter), similar to that which we use in aircraft. The ELT is activated when in the sea, its position located by satellites, which are permanently monitoring the ELT frequency world-wide.

I am sure the thoughts of the whole nation are with those that have lost there loved ones in this tragedy.