The EM-HD-NCP acts as an HDMI monitor by emulating the EDID found in a typical HDMI LCD and by asserting the HPD (Hot Plug Detection) to the HDMI video source. Most PCs and laptops require a special handshake from the display before they output video. This handshake involves reading the EDID table from the monitor. The EDID contains information such as Native or supported resolutions and Video Formats. Some older equipment may not support the EDID properly and the end result is that you often can't get video from your PC to external display.