Shunt trip breakers operate with the same functionality of a standard type breaker providing over current and short circuit protection, as well as switching capability. The shunt trip breakers provide an additional function in that it can be tripped remotely through the use of a built in magnetic coil that can be energized to trip the breaker. Each shunt trip breaker will have an additional 1-Inch pole attached to it to house the magnetic coil. The additional pole does not plug onto and is not energized by the bus bar. Siemens strongly recommends against the use of "used" breakers. The installation of used breakers in a Siemens panel will void the **on the panel. Siemens does not sell used breakers and has not approved any 3rd party sellers to do so.