Black Box DVI Matrix Switch with Audio and RS232 Control - 4x2 , GSA, Routes 4 different DVI and audio signals to 2 different DVI monitors and speakers. Ideal for digital signage display systems where you want to switch source inputs for screen output on various screens. Switch using buttons on the front panel, with a PC connected via its RS-232 port, or by using the wireless remote control from up to 16.4 ft. (5 m) away.