A metal frog that carries current and changes polarity with the turnout setting. Locomotives with a short wheelbase run over it better than over an insulated plastic frog.
Peco Streamline SL-E191 has a live frog (Electrofrog); SL-91 has an insulated frog (Insulfrog). Both diverge 12° on R610.
Peco Streamline 00/H0: articles, geometry and the track planner