See here for some discussion as to why you should NOT rely on this method for something as important as 911.
is there a pot this guy *doesn't* have his fingers in? =)
Besides, if you are running VoIP through your phone lines, you would need to physically disconnect the POTS line at the Network Interface Device (NID) anyway.
not doing that, but good point. mine is run thru cable internet then wireless broadcast to handset from a base unit.
panasonic tgp500 -- nice device.