The Mono Frog Juicer is an automatic polarity reverser for a single frog. Setup is simple, connect two wires to the DCC bus and one wire to a frog. The frog should be fully isolated. When a train crosses the turnout and the frog is the wrong polarity, the frog juicer will reverse the polarity so quickly that the train and the rest of the DCC system will never notice.
This unit should not be used with boosters over 5 Amps; see the Dual Frog Juicer for 10 Amp boosters. DCC only.
See here for full details https://www.tamvalleydepot.com/images/Mono_Frog_Juicer_Manual_v2.pdf