You're correct it is the ELT not the transponder... duhhh...

Matt wrote:

I think you are referring to the ELT battery right? That needs to be
replaced every 2 years.


"Jon Kraus" wrote:

Yea, there is a battery in the trasponder that requires replacement every
2 years whether it needs it or not. It is used to power the unit in the
event of a crash and no power from the ship is getting to it. The new
models use regular "D" cells while older ones (like mine) require a
proprietary battery for about $40.