"RB" wrote in message
. ..
What function does the internal battery in marine lorans play? Does it
power a residual memory core for when the set is off?

Yes, that's pretty much the idea but all models are not equal. Among the
more useful data stored can be the last used loran chain and slave stations,
manually or automatically entered waypoints, time and date, any manually
entered correction factors, and...... and........ there must have been more?
Old Chief Lynn