Efficient usage of available spectrum is increased by logically dividing government licensed frequency channels into sub-channels, each of which can individually transmit a signal between a base unit and terminal. Either a first storage unit or a second storage unit is attached to the image forming unit. The device may be furnished as an independent product, as an integrally formed or molded segment of a primary product, or attached to rigid or flexible substrates. The methods may include receiving and validating licensing requests. The light-absorbing material of the present invention has a structure represented by Formula below:X\u2014Y\u2003\u2003. The opening portion of the built-up layer has a tapered portion tapering toward the outermost surface of the built-up layer.