4-Port HDMI (4K/60Hz) Ultra-HD KVM switch w/ USB 2.0 hubs and audio support.


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Video Type: HDMI (up to 4K/60Hz)
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The SmartAVI SM-UHN-4S (formerly UHDN-4PS) is a 4-port, single-head HDMI 2.0 KVM switch with Ultra-HD 4K/60Hz resolution video emulation. It can control keyboard-mouse functions on up to four remote computers, and emulates video from HDMI source devices.

SM-UHN-4S Use Diagram
SM-UHN-4SBack Panel

SM-UHN-4S Features & Benefits

  • Supports up to Ultra-HD 4K (3840x2160) @ 30/50/60Hz.
  • Supports 3D.
  • Supports LPCM, Dolby-AC3, DTS7.1, and DSD/Dolby TrueHD/DTS-HD master audio.
  • Supports HDMI 1.3, 1.4, & 2.0.
  • HDMI and HDCP compliant.
  • Control up to four computers with a single KVM.
  • Full EDID HDMI video emulation.
  • Zero pixel loss with TMDS signal correction.
  • Supports USB Keyboard-Mouse emulation. (basic function only)
  • Supports all USB 2.0 devices - through transparent hub)
  • Rack mountable in a standard 19 inch rack (rackmount kit sold separately)
  • Hot key commands for quick channel selection.
  • Independent (asynchronous) switching of KVM and peripheral USB ports. Users can scan a document and save in another computer.
  • Complete KVM emulation for error free booting.
  • Easy switching via front-panel, RS-232 or hot keys.
  • Full HDMI support, backwards compatibility.

SM-UHN-4S Package Includes

SmartAVI SM-UHN-4S Package Contents

  • (1) SM-UHN-4 4-Port Ultra-HD 4K/60Hz KVM Switch
  • (1) Power Supply
  • (1) Quick Installation and User Guide

SmartAVI SM-UHN-4S (formerly UHDN-4PS) Specifications

Link Rate5-4 Gbps
Input Interface(4) HDMI 2.0 Female
Output Interface(1) HDMI 2.0 Female
Resolution480i to 4Kx2K @ 60 Hz (YUV420)
Input EqualizationAutomatic
Bandwidth300 MHz, 10.2 Gbps
HDCP CompliantYes
Max Cable Length40 ft. (Dependent upon quality)
Input(4) 3.5mm Stereo Audio Jack
Output(1) 3.5mm Stereo Audio Jack
Frequency Response20Hz - 20KHz
Nominal Level0.0 - 1.0 V
Common ModeRejection @ 60 db
Signal TypeUSB 2.0, 1.1 and 1.0 w/ internal hub
Input Interface(4) USB Type B Female
Output Interface(2) USB 1.1 Type A for Keyboard and mouse; (2) USB Type A Transparent
Front PanelButtons
RS-232Via SmartControl @ 9600 bps
Hot KeysVia Keyboard
EmulationKeyboard, Video, Mouse
PowerExternal 100-240 VAC/ 5VDC4A @ 20W
Consumption20 W (Max)
Dimensions2"H x 5.75"D x 12.75"W
Weight3.55 lbs
ApprovalsUL, CE, ROHS Compliant
Operating Temperatures23 to 95°F (-5 to 35°C)
Humidity5 to 90% RH, non-condensing

The SM-UHN-4S is formerly known as the UHDN-4PS

Question: Specification say that it has only 10.2 Gbps bandwidth and HDMI 1.4 ports. How this device can handle UHD resolution with 60Hz if its required 18 Gbps?
Answer: Thank you for inquiry,

SmartAVI by design limits HDMI transmission to video and audio - some of the less used and more theoretical features in HDMI (i.e. ethernet), are stripped out. The combination of the previously mentioned and the way they they handle the video/color formats (4K UHD@60hz 4:4:4 - 12 bit, pixel clock of 340 Mhz) allows you to run 4K UHD @ 60HZ with as little as 6Ghz of bandwidth. However note, the vendor had a typo on their product page - the SM-UHN-4Q-S actually uses HDMI 2.0 instead of 1.4.

Please let us know if there is anything else we can help you with, or if you would like a recommendation based on your application.

Question: Can the the USB wires for keyboard and mouse be prolonged to up to 10 meters (32 feet) by using 2 active extension cables of 16 feet which identify themselves as a USB hub? Are USB hubs supported for keyboard and mouse connection?
Answer: Thank you for your inquiry,

You could theoretically use a simple USB Hub Extender for each keyboard-mouse (USB-HID) port separately. Not all USB Hubs would supported though: the hub should be powered locally (rather than through the KVM), like this NTI USB extender, and should be fully transparent, such as Icrons patented ExtremeUSB Extenders.

You would not however be able to extend both the keyboard and mouse on the same port: The SmartAVI SM-UHN-4Q-S features USB emulation for the Keyboard and Mouse ports (USB-HID) to prevent any lag in operation, to keep the devices synced, and to prevent any dropping of the devices. This in combination with the USB-HID standard used in Keyboard and Mouse ports would consequently prevent non-'transparent USB' devices, multiple devices in 1 port, and non-'USB-HID' devices, in those keyboard and mouse ports.

For any peripheral USB devices that you would like to extend from the KVM, the SmartAVI SM-UHN-4Q-S does also feature (2) USB Hub ports that you can plug ANY USB device into, including USB hub extenders.

Question: 2 questions: 1. Is audio only supported by the 3,5mm jacks or also by HDMI? and 2. Is a smartcard-reader keybord supported? Is not only the keyboard visible in windows but also the smartcard- reader?
Answer: Thank you for your inquiry,

The SM-UHN-4Q-S carries audio over the 3.5mm jack (AUX <- independently switchable) as well as over HDMI ('HDMI-Embedded' <- switches with source).

SM-UHN-4Q-S compatibility with a smartcard-reader keyboard would depend on how the keyboard is implemented:
Separate USB connection for smartcard-reader:
An external or internal smartcard reader with a separate USB connection from the keyboard would absolutely be supported. Plug in the Keyboard into the keyboard USB port, and the other USB connection into one of the (2) USB hub ports. You are good to go! Both USB hub ports are transparent, so any USB device will function normally.
Single USB connection for keyboard & smartcard-reader (integrated):
A keyboard with an integrated smartcard reader (connection over a single USB) cannot be plugged into the keyboard port due to the USB-HID emulation used for that port (provides quick & reliable source switching). However, some users have had success plugging-in advanced keyboards into one of the (2) USB Hub ports, and then either leaving the keyboard port empty or plugging-in a second keyboard (to ensure that the KVM realizes there is a keyboard; this second keyboard can either used for switching or just left aside). That being said, this is still a hit or miss proposition, and if it does work, it may lead to some loss in functionality such as hot-key switching. For the most reliable switching and best compatibility, we would still always suggest using a standard keyboard with a KVM Switch.

Question: Would this support 1080p at 120Hz and 3840x2160 at 30Hz? Or does it only support 60Hz as per the resolution specifications?
Answer: Thank you for your inquiry,

The SmartAVI SM-UHN-4Q-S does indeed support 3840x2160 @ 30Hz (30/50/60Hz). The SM-UHN-4Q-S would also theoretically support 1080p @ 120Hz, but we are unable to guarantee this piece (yet to be tested).

Question: Is this a true KVM in that the video signal is maintained to all attached machines or is the video switched? (That is, the video signal is dropped to all but the current selection.)
Answer: Thank you for your inquiry,

The SmartAVI SM-UHN-4Q-S does indeed maintain the signal to all attached machines - The unit features Full HDMI 'EDID video emulation', which constantly pings for the video settings, ensuring quick and reliable switching between the attached machines.

Question: Hello, are there plans to include USB 3.0 in the SM-UHN-4Q-S model?
Answer: Thank you for your inquiry,

"UHDN" is fairly new series from SmartAVI. While it is possible that they will release an updated version including USB 3, we are not currently aware of a upgrade road-map.

In the meanwhile, you can always visit our USB 3 KVM Switches page for alternative options for your application.

Question: What is the difference between the SM-UHN-4Q-S and SM-UHN-4Q-S?
Answer: Thank you for your inquiry,
  • SM-UHN-4Q-S is the part number for the KVM Switch
  • SM-UHN-4Q-S (or SM-UHN-4Q-S) is the part numbers you would order, which includes:
    • (1) SM-UHN-4Q-S KVM switch
    • (1) Power Supply
    • (1) Quick Installation and User Guide

Question: Is there also a KVM-switch 4K 60Hz HDMI for 2 computers? What are the extra costs shipping this article form USA to the Netherlands?
Answer: Thank you for your inquiry,

I am not currently (3/20/2018) aware of a 2-port HDMI KVM switch that would support 4K at a 60Hz refresh rate. That being said, you can use a 4-port KVM switch, like this SM-UHN-4Q-S, and plug in only 2 of the ports.

Please refer to our International Order policy for more information on shipping this unit to the Netherlands.

Question: Does the SM-UHN-4Q-S support 4K 60Hz RGB(YCbCr 4:4:4) 10-bit?
Answer: Thank you for your inquiry,

While it does support 4k60 RGB, it only supports the 8 bit variant.

For a KVM that supports 4K 60Hz RGB(YCbCr 4:4:4) 10-bit, you may want to consider the Aten CS1924 DisplayPort KVM as an alternative.

Please let us know if there is anything else we can help you with!