( ( ( Cracked , ) ( worn ( electrical ( wiring insulation ) ) ) ) . )
(ROOT (NP (NP (NNP Cracked)) (, ,) (VP (VBN worn) (NP (JJ electrical) (NN wiring) (NN insulation))) (. .)))
Cracked, worn electrical wiring insulation.
(ROOT (S (NP (JJ Electrical) (NNS wires)) (VP (VBP are) (ADVP (RB usually)) (VP (VBN covered) (PP (IN with) (NP (NN plastic) (CC or) (NN rubber))) (S (VP (TO to) (VP (VB insulate) (NP (DT the) (JJ electrical) (NN wire))))))) (. .)))
Electrical wires are usually covered with plastic or rubber to insulate the electrical wire.