( ( This ( shunting action ) ) ( ( causes ( ( track circuit ) ( voltage ( to ( ( ( ( short-circuit and ) prevent ) ( electrical energy ) ) ( from ( reaching ( the ( control relays ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This) (VBG shunting) (NN action)) (VP (VBZ causes) (SBAR (S (NP (NN track) (NN circuit)) (VP (VBP voltage) (S (VP (TO to) (VP (VB short-circuit) (CC and) (VB prevent) (NP (JJ electrical) (NN energy)) (PP (IN from) (S (VP (VBG reaching) (NP (DT the) (NN control) (NNS relays)))))))))))) (. .)))
This shunting action causes track circuit voltage to short-circuit and prevent electrical energy from reaching the control relays.
(ROOT (S (NP (PRP We)) (VP (VBP use) (ADJP (JJ voltage) (S (VP (TO to) (VP (VB keep) (NP (NP (NN track)) (PP (IN of) (NP (JJ electric) (JJ potential) (NN energy))))))))) (. .)))
We use voltage to keep track of electric potential energy.