Multifunctional transmitters capable of transmitting signals of different specifications in different modes are provided, in which N output units are provided and each output unit comprises a serializer and an output driver. A control unit, according to a mode selection signal, selects a first set of output units from the N output units to transmit a first video data compatible with a first transmission interface under a first transmission mode and selects a second set of output units from the first set of output units to transmit a second video data compatible with a second transmission interface which is different from the first transmission interface under a second transmission mode.