A mini-breaker is a thermal cutoff (TCO) device that combines overtemperature and overcurrent protection in a single, compact package. It is an ingenious combination of two common circuit protection technologies: a PTC and a bi-metal switch. It has two key terminals for conducting current: the arm terminal and base terminal, which are connected in a normally closed position to allow current to flow through the device. The contact point between both terminals is critical and a testament to the high precision of the Bourns mini-breaker in that the contact resistance in some model families is as low as 1 mΩ max.