Tony: Peco make 2 types of points -- Electrofrog and Insulfrog. The Insulfrog have a plastic frog (place where the rails cross a.k.a. common crossing). Both of them can kill your circuit but different ways.
Picture a loop of track with one point making a siding inside. The electrofrog point is all rail. when you turn the point to the siding, the rail connects the frog to the outside rail, causing a short circuit (all the way around the layout to your feeders.) Whne you turn the point to the loop, the two rails on the siding are the same polarity, and nothing runs on the siding. The short is cured with a plastic rail joiner between the frog and the feeders.
With Insulfrog, the point that doesn't touch the stock rail is neutral -- open circuit. If it's set for the loop, the rails in the siding are one live, one dead. Siding is dead. If it's set for the siding, NO PROBLEM. The inside rail current does not meet the outside rail. You can even run a train through it and just have a derailment.
You said something about a reversing loop. That's a topic for another day.