Underwater Locator Beacon ( ULB )
An ULB is directly attached to the front panel of the DFDR. The beacon actuates on immersion in water down to a depth of 6000 meters.It has a detection range of 1800 to 3600 meters.You can service the ULB without disassembly of the DFDR. Maintenance has to be performed at determined time intervals to replace the battery of the ULB .
Same ULB is on the CVR.
But no position sent by ELT, so the ULB has a really small range to get find easily.