I bought an old system which has two 121 mhz wearable, water-activated transmitters, and an alarm/directional receiver.
If someone falls
overboard, an
alarm sounds, and you point the receiver to get the direction to the victim. Old, crude, but the basic functionality is more or less correct.
Theoretically the new
AIS SARTs should be a great leap forward, since they give not only direction, but lat-long of the victim. Besides that, they require no special receiver -- any
AIS receiver will do.
The only problem is that they are all manually activated. What if the victim is a frightened child, or an unconscious person? Then that's as good as useless.
I actually think
VHF DSC might be the better technology for this use. How about a device which:
1. Is wearable, with
water activation, and water-activated
antenna deployment.
2. Sends a
DSC distress message when activated, and repeats it with updated position.
3. Can be interrogated by DSC -- Position Request/Position Report protocol. So even if it doesn't go off automatically, you can interrogate it and get the position of the device -- and this doesn't set off alarms everywhere, either, in case it's not an
emergency.
The last function particularly useful in case of
children -- you don't know where they are, they may or may not be in trouble, you don't want to set off alarms if there is no
emergency, but you really want to be able to see where they are.
What do y'all think? Maybe someone would make such a device?