Abstract: Provided is a digital image transmission system in a high definition multimedia interface (HDMI) format or a digital visual interface (DVI) format. A transmission and reception reinforcement device of the digital image transmission system includes a transmitter, a receiver, and a power supply circuit. The power supply circuit includes a first power supply unit supplying power to the transmitter and a second power supply unit supplying power to the receiver. Power output terminals of the first and second power supply units are connected to each other. External-power supply voltages respectively input to the first and second power supply units are output to the power output terminals. When all of the external-power supply voltages input to the first and second power supply units are lower than a predetermined voltage, an internal-power supply voltage present in a communication line between the host device and the display device is output to the power output terminals.

Abstract: An optical communication interface module connected to a direct-current (DC) power terminal, an input/output (I/O) terminal and a ground terminal, to perform optical communication. The module includes a PNP transistor for transmission, a pull-up device, a photo generator device, a photoelectric converter, and first and second NPN transistors for reception. The PNP transmission transistor has its base connected to the I/O terminal and its collector connected to the ground terminal. The first transistor for reception with its collector connected to the anode of the photo generator device and its emitter connected to the ground terminal, has its base driven by output signals of the photoelectric converter. The second transistor for reception with its collector connected to the I/O terminal and its emitter connected to the ground terminal, has its base driven by an output signal of the photoelectric converter.

Abstract: An optical communication interface module includes a combined transmission module and a combined reception module. The combined transmission module processes a D+ electrical data signal and a D? electrical data signal, and combines and transmits the same through a first optical fiber line. The combined reception module processes the D+ and D? electrical data signals combined and received through a second optical fiber line, and applies the D+ and D? electrical data signals to a D+ port and D? port, respectively. The combined transmission module includes a transmission driving circuit that generates an optical data signal corresponding to one of the D+ and D? electrical data signals, and a transmission control switch that controls the optical data signal to have a level of brightness higher than a first set value while the D+ and D? electrical data signals are both maintained at a logic ‘low’ state, and controls the transmission driving circuit.