Power distribution units (PDUs) have an electrical input and several outputs, often as electrical outlets, for powering multiple devices.  They typically contain features such as circuit breakers and transient voltage suppression.  Unit types can be modular or desktop, monitor shelf, plug strip, cabinet or cabinet mount, rack mount, vertical mount, wall mount, or hardwire mount.  The number of outlets in the power strip or power distribution unit (PDU) also refers to the number of outputs if not in the form of AC outlets.  Outlet configurations can be NEMA, IEC, CEE, or JIS.