English: X-band microwave circulator. This is a device with three ports, with flanges to attach to waveguides. It has the property that microwave power input at one port only comes out the next port to clockwise. The circular arrow on the label indicates the direction that power travels. It is made with magnetized ferrite material. In this example a matched load resistance is attached to the righthand port. Therefore microwaves entering the bottom port (labeled INPUT) will come out the top port (labeled OUTPUT), but microwaves entering the top port will be absorbed in the load.