 
 <prompt> Wetin be circulators? Based on di previous question, write one context wey contain di answer. E fit be 1 - 20 sentences. Context: <response>: ```One important thing wey dey needed for the reciprocity property wey we talk about na say the materials wey dey inside the antenna and transmission medium must dey linear and reciprocal. Reciprocal (or bilateral) mean say the material dey respond the same way to electric current or magnetic field whether e dey go one direction or the opposite direction. Most materials wey dem dey use for antennas dey meet these conditions, but some microwave antennas dey use high-tech components like isolators and circulators, wey dey made of nonreciprocal materials like ferrite. Dem fit use these things to make the antenna behave differently when e dey receive compared to when e dey transmit, and this fit dey useful for applications like radar.``` 