A method for transmitting a transmission time interval signal in a cellular network is described. The operational cooling device is thermally coupled to a heat pipe. Therefore, signals can be attenuated by the attenuation control circuit, in addition to the attenuation circuit. First to fourth control gate line drivers are arranged in each of local driver areas between which two adjacent small blocks are disposed. An antenna, screws, power switch, charging receptacle and all mounting hardware are included. Therefore, it is possible to provide a frequency modulator that can use a reference signal source having no frequency modulation function, and perform modulation over a wide range of frequencies based on a digital modulation signal.