ELT vS ELB
ELT operates 21.5/243/406 mhzs The last freq contacts a satellite monitoring system. It uplinks the serial No of the Box which the Sat authority use to look up the Regulatory authority which keeps a list of serial no's versus tail no.s
Some ELT's are tied into the Nav sys to uplink last position. Many rely on the Sat system to direction find the signal
ELB operates when in contact with water to output Ping to allow the CVR & FDR to be recovered
An ELT due to the frequencies involved is not able to contact the satellite from underwater. It is also not a waterproofed box