On Wed, 17 Jun 2015 14:54:37 -0700, John Good wrote:

121.5 mHz ELT: location accuracy 12000 meters

I'm not sure how to interpret this. An ELT (of any flavor) transmits a
continuous signal, for as long as the batteries hold out. It can be
received at a range much greater than 12 km, and can lead a searcher to
within a few meters of the ELT.

I took that as how accurately the old satellites could locate a 121.5 Mhz
signal. Took several orbital passes.