Novel piperazine and homopiperazine derivatives are agonists of melanocortin receptor and are useful for the treatment, control, or prevention of diseases and disorders responsive to the activation of the melanocortin receptors. In an RFID card, a magnetic field strengthbrightness conversion section adjusts the brightness of two LEDs in accordance with the detected magnetic field strength of a carrier wave. The exterior surface has an upper portion generally defining a portion of a cylinder, and a lower portion generally having a rectangular block shape.