In 15 years of work on large commercial transport aircraft I´ve never seen an ELT installed in either the DFDR or the CVR. They certainly have no antenna attached to them either. Obviously a large aircraft wreck on land has a certain chance to be found by using optical means (Mark 1 eyeballs). For crashes into the sea both recorders have an underwater locator beacon attached to them, which will emit "ping" signals when immersed in water.
Jan