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Could you do tests with a simplified setup, without a splitter/extender and see if duplicating works, then, for a test?
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Could you do tests with a simplified setup, without a splitter/extender and see if duplicating works, then, for a test?

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In an environment in which a desktop computer is using an Nvidia GTX 1050 video card, a Dell monitor is plugged into this card's DVI port. &nbsp;From the HDMI next to the DVI port, an HDMI cable is going to an Inland HDMI 5 port splitter's HDMI In port from the HDMI outport an HDMI cable is going to an Iogear cat5 HDMI extender to two Vizio televisions. &nbsp;A program titled Media Shout is installed that requires the computer to be set to Extend displays and works fine. &nbsp;But for some reason if we want to Duplicate the display, the television screens go black.
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In an environment in which a desktop computer is using an Nvidia GTX 1050 video card, a Dell monitor is plugged into this card's DVI port.  From the HDMI next to the DVI port, an HDMI cable is going to an Inland HDMI 5 port splitter's HDMI In port from the HDMI outport an HDMI cable is going to an Iogear cat5 HDMI extender to two Vizio televisions.  A program titled Media Shout is installed that requires the computer to be set to Extend displays and works fine.  But for some reason if we want to Duplicate the display, the television screens go black.

Why would extend functions on Windows 10 work and duplicate functions do not?

Windows 10 is a personal computer operating system featuring the "universal application architecture" (UAP); apps can be designed to run across multiple devices with nearly identical code, including PCs, tablets, smartphones, embedded systems, Xbox One, Surface Hub and HoloLens. Windows 10 also includes a virtual desktop system, a window and desktop management feature called Task View, the Microsoft Edge web browser, support for fingerprint and face recognition login, voice-based search (Cortana), new security features for enterprise environments, and DirectX 12 and WDDM 2.0 to improve the operating system's graphics capabilities for games.

Windows 10

This topic area includes legacy versions of Windows prior to Windows 2000: Windows 3/3.1, Windows 95 and Windows 98, plus any other Windows-related versions including Windows Mobile.

Windows OS

A monitor or a display is an electronic visual display for computers, usually comprised of the display device, circuitry, casing, and power supply. The display device in modern monitors is typically a thin film transistor liquid crystal display (TFT-LCD) thin panel, while older monitors used a cathode ray tube (CRT) about as deep as the screen size. They are connected to the computer via VGA, DVI, DisplayPort, Thunderbolt, LVDS or other proprietary connectors and signals.

Displays / Monitors

A desktop computer is a personal computer designed for use at a single location due to its size and power requirements, usually by one person. The most common configuration has a case that houses the power supply, motherboard, disk storage (usually one or more hard disk drives and optical disc drives); a keyboard and mouse for input; and computer monitor and printer for output. The case may be oriented horizontally and placed atop a desk or vertically and placed underneath or beside a desk.