A “polymeric positive temperature coeffecient device”, commonly called a PPTC, differs from fuses and circuit breakers in that they don’t actually “break” (open) a circuit when a fault is present. Under normal operating conditions, they are in a very low resistive state. When a circuit fault is present, they change to a highly resistive state; however, a very small amount of current still flows through the device to keep it latched in the highly resistive state. Once the circuit fault is corrected, the PPTC cools and returns to its very low resistive state. Unlike thermal circuit breakers, PPTC’s do not need to be reset manually (no buttons to push) – they automatically reset themselves when the circuit fault is corrected. PPTC’s are also much cheaper than thermal circuit breakers and much easier to source.