KVM
From DIGITUS - Wiki
This article is about DIGITUS® KVM switches.
Here on our web site you can get a product overview.
General information
DIGITUS® KVM devices (Keyboard, Video, Mouse) are used to connect 2 or more computers with one input/output unit (keyboard, mouse, and monitor). Some versions of our KVMs also allow you to redirect USB connections and audio functions in addition.
Special characteristics
- KVM devices exist as desktop versions and as pocket versions.
- Some KVM devices feature external power supply options. Often they also function without additional power connections.
- Other KVM devices are completely currentless. They tap electricity via a PS2 o r USB cable.
Troubleshooting
KVM only offers PS2 connections - computer has only got USB connections
Generally we suggest you not to use USB-to-PS2 adapters, for this often causes problems. If you still want to use an adapter, you might want to try a DA-70118 adapter, which is an adapter most likely to work with KVMs.
After shutting down the computer the KVM switches to the next port available
- Problem description: Usually this is a normal reaction. Yet, if two PCs are connected and both are shut down the situation might also occur that the KVM changes to the other computer which is also switched off.
- Background: The KVM is informed via a PS2 or USB connection that one PC is switched on / available. Whenever in this situation a computer switches off power supply on its PS2 or USB connection by shutting down whilst the other one does not, the KVM will switch automatically to the connection with an electric signal.
- Solution: Some BIOS versions allow you to make one of the following settings: Power on USB or Power on PS2. Then the computer will not switch off power supply of USB ports / PS2 ports, which allows you to start your PC by moving your mouse, pressing a key on your keyboard, or using other devices connected in a specific way. You can use this property of your system in order to operate your KVM in a certain way.
PC needs 5 minutes in order to start up in POST mode
- If you use USB KVMs offering PS2 and USB connections for computer connections, please either use USB or PS2.
- Sometimes it is necessary to change the BIOS settings for the P.O.S.T. process. In this case the "Halt on" or HPET settings in the BIOS mode are especially important.
- If both solutions do not help you solve the problem, please ask the manufacturer of the mainboard of your PC to find out if there approaches to solving a problem. Please tell us how you solved your problem..
KVM does not function with a VGA<>DVI adapter OR My VGA KVM shows no image on my DVI monitor
- Please note that whenever DVI/analog KVMs are used only those signals with a contact are processed. A DVI-D (digital) monitor will not show an image if you connect e.g. a DVI-A (analog) signal with a DVI-I KVM device.
- If you use VGA->DVI-I adapters, please make sure to use active versions of these adapters if your monitor exclusively supports DVI-D (99% of all DVI monitors are DVI-D monitors, not DVI-I monitors).
- If DVI-I KVMs are used featuring mixed input operation (one PC connected via VGA, one PC connected via DVI), please make sure that the connection cables as well as the monitor support DVI-I operation.
Here is a graph about the connection possibilities mentioned above.
No image is shown, PC does not start up at all
If you use KVM switches with PS2 you have to make sure that the devices are connected in a currentless way. This means that the computers and the monitor must not be switched on. We recommend you to disconnect your equipment from the in-house mains. According to PS2 specifications PS2 ports are - different from USB devices - "not hot-pluggable". This does not only concern the ports of a computer, but also connections of input devices connected with the KVM itself. If these aspects are disregarded this might cause malfunctions of PS2 controllers, either of the controller built in the KVM device, of the one built in the PC, or of both controllers. Please also note that you have to use the right KVM cable.
KVM device does not recognize a PC connected with KVM
Please connect the keyboard plug with the PC. The connection between the keyboard plug and the PC ensures that the KVM device is supplied with voltage input which allows you to use the KVM for switching purposes. A KVM device connected without a mouse and without a keyboard is called a Selector.
KVM does not keep changes of hot keys
Whenever a computer disconnects a PS2 / USB connection from current supply the KVM is no longer supplied with electricity. Thus it is reset to its delivery condition. Those KVM devices which optionally can also be operated with current can be equipped with a power adapter. This will solve the problem.
Keyboard does not have a scrolling key anymore
Some of the newer keyboards do not have a scrolling key any longer. Yet, some KVM devices need these keys to switch. There are two approaches to solve this problem:
- Use the CTRL key to double click. This will, however, not work with every KVM!
- Connect another keyboard featuring a scrolling key with the KVM and make an adjustment (e.g. Scrolling-Scrolling-NUM, Scrolling-Scrolling-PRINT, or Scrolling-Scrolling-Shift key(Caps lock)).
A KVM featuring a PS2 port draws via this connection "upkeeping power". that is why at least one computer should not be switched off completely, for otherwise the KVM will be set back to its original state.
If no reprogrammed Hot Key is used there is no general problem.
Some KVM devices also feature an option to connect an external power supply. These types of keyboards will keep their settings and all computers connected may be switched off completely.
PC will not start up, error message "Keyboard not present"
Select "All (errors), but Keyboard" via "Halt on" in the standard setting of the computer´s BIOS. This means: Do not wait for the keyboard, but just take a standard keyboard for granted. Sometimes it may be necessary to use the optional power supply. Mainboards which do not offer this setting might have a setting for H.P.E.T. instead, which in this case should be activated.
USB hub function is not supported, printer does not work when connected with the KVM
If a USB device is operated with a KVM (e.g. DC-11201-1) the problem might occur that USB devices cannot be recognized or infrequent malfunctions occur. If the KVM device features an optional power connector the KVM device should in this case be operated together with a respective power supply, as it is also described in the Manual.
Only one computer recognizes keyboard and mouse
Some KVM switches offer a special function allowing you to block the USB port to ensure that e.g. data transfers via a USB stick are not interrupted if you just want to have a "quick look" at what is going on with the other computer.
This function is called Auto Switch function. Auto Switch is only available in KVM devices with an integrated USB hub.
The "Auto Switch" function can be activated by pressing one of the KVM device´s shift keys for quite some time (longer than 5 sec.). As a consequence the LED will now follow the changeover switch.
Keyboard cannot be recognized, additional options do not function
Special keyboards like gamer pad keyboards, KVK chip reading keyboards, and wireless versions of keyboards might cause problems. We do not recommend the use of such keyboards. Thus we cannot support you if you have technical issues with these devices.
If you intend to use Logitech devices, please read the respective articles concerning our KVM in order to find out if certain Logitech devices are explicitly supported by our products.
In some cases keyboards consume too much power. If your KVM device does not have an optional power port a keyboard which is not recognized cannot be operated with this KVM device. In this situation it might help you to purchase a KVM device with an integrated hub (a KVM which does not explicitly specify where to plug in your mouse and keyboard).
Mouse is not recognized, is lagging
- As a basic principle standard mouse devices are supported. Mouse devices for gamers with four and more pushbuttons, wireless mouse devices and laser mouse devices starting from 1600 DPI might cause problems.
- It is known in few cases that a mouse which is operated via a KVM does not work together with the computer hardware. The same cable sets with other PC hardware components work trouble-free. If such a case occurs the mouse should be connected separately with the PC or another mouse device should be used. In some cases the mouse software of the manufacturer directly accesses the mouse itself. Thus, these devices cannot be used with a KVM device.
- If KVM extenders are used the use of shielded cables or the distance could be the problem.
These options which were mentioned do not necessarily have to refer to KVM devices with an integrated hub (KVM devices which do not explicitly specify where to plug in your mouse and keyboard).
Gamer mouse devices / keyboard / PAD / Wireless USB keyboards / mouse devices
Mouse devices for gamers, keyboards for gamers, game pads, or devices with a high data transfer rate should only be used with those KVM devices additionally offering integrated USB hub functionality
Gamermäuse, Gamertastaturen oder Gamepads oder Geräte, die einen hohen Datentransfer haben sollten nur an KVM's mit integriertem USB-Hub (KVM devices which do not explicitly specify where to plug in your mouse and keyboard). Yet, we cannot offer you a warranty that these devices work with our KVM products.
The following KVM devices work frequently:
- DC-11201-1 (2-PC)
- DC-12201-1 (4-PC)
Adapter does not function with mouse / keyboard
It cannot be warranted that adapters work together with KVM products.
KVM keeps on changing over to various monitor screens
Possibly the "Auto Scan" mode was activated. You can disable this mode by pressing the [Esc] key.
Color distortions at monitor screen
- Many of the KVM devices sent back to us turned out not to be defective, but either their cables were broken (10%) or wrong cables were used (90%).
- DVI models must not exceed an overall cable length of 10 meters. This also includes CU cables!
- In cases of KVM extenders the use of shielded cables or the distance might cause problems. We recommend you to use UTP cables.
Wrong cable set
Our KVM products can usually be bought in two versions. The part number of the second product is identical with the part number of the first product. It end, however, with -1, which indicates that a cable set for two devices is already included in the scope of delivery.
There are three possibilities to find out the correct cable set for your KVM product:
1. Visit our web page KVM and Cable Sets in the wiki.
2. Ask your well-assorted local retailer where you bought the KVM devices.
3. Select the tab "Catalogs" at the [www.assmann.com ASSMANN] web site. There you can download the full catalog or only the chapter Datacom and KVM Switches.
To give you an example (this might vary from year to year):
There you can find the product DC-11202-1 which already includes 2 cable sets. It also includes notes that
1 - the cable types K6 and K7 can be used
2 - you can find these cable types on page 105.
On page 105 you can find the part number of cable type K7, "AK 82004", and the part number of cable type K6, "AK 82002".
Wrong cable type
Even if cable sets of third-party suppliers look similar to ours and work in 1.8 meter versions longer cables might cause troubles regarding the image quality. Please use only original spare parts/accessories for Digitus KVM devices, for then you can be sure that you do not purchase aluminum cables (CCA) or steel cables (CCS), but copper-based cables (CU) of a higher quality. This will ensure a better image quality if you use higher screen resolutions.
We received emails from monitor manufacturers (also from well-known companies) stating that there were incompatibilities with original cables by monitor manufacturers which were enclosed with these products as CCS versions and could not be operated together with any types of extension cables. In such cases we recommend you to use a CU cable of a higher quality in order to connect your KVM with the monitor.
PIN assignments of other manufacturers might differ from the original PIN assignments.
Pushing scrolling wheel and right/left mouse button changes "active" computer
Some parts of the "Basic" series of our KVM switches, which actually do not have a mouse clicking function, react like that. In order to switch off this feature, e.g. if you intend to use CAD applications, please follow these steps: -quickly double-click the -Num Lock- key on your keyboard (the -Num Lock-, -Caps Lock-, and -Scroll Lock- LEDs light up to indicate the command mode) a) press -left Windows key- or -central mouse button- + -left mouse button- in order to disable "mouse clicking function" b) press -right Windows key- or -central mouse button- + -right mouse button- in order to enable "mouse clicking function"
Wireless keyboards or mouse devices do not function
The data transfer rate of wireless mouse devices, of wireless keyboards, or of combinations between wireless mouse devices and keyboards is too high so that in many cases they cannot be supported by KVM devices. Even if such a combination of input devices and KVM devices worked one time they might no longer operate together after an update of the operating system or of mouse / keyboard drivers. Thus we cannot offer you support for wireless input devices.
KVM switches / hot keys
In some of the latest keyboard versions a rebound protection is integrated. This means that if the shift key is pressed twice it is "double-clicked" though the keyboard allows only one stroke. In this case it might be necessary to press the shift key three times. In all cases pressing the hot key several times means here that all of this must happen within a second.
Hotkey variant 1
[Ctrl]+[Ctrl] (press the keys in quick succession) + [1...8] Switch to the PC of your choice
Hotkey variant 2
[left Ctrl]+[left Ctrl] (press the keys in quick succession) Switch to the next "smaller" PC (2>1) [right Ctrl]+[right Ctrl] (press the keys in quick succession) Switch to the next "bigger" PC (2>3)
Hotkey variant 3
Just like variant 1, but the [scrolling] key replaces the [Ctrl] key.
Switching / changeovers via hot keys
Double-click the hot key as it was set in the settings, then press new hot key (NUM, PRINT, Shift lock/Caps lock, Ctrl). (You have got a period of time of 1-3 seconds for the whole process).
Example: Scrolling-Scrolling-NUM changes hot key Scrolling to hot key NUM.
Please note that changes of your hot key will only last as long as at least one PC supplies the KVM with power. Usually PCs still send - even when they are switched off - an electrical power signal to the USB and PS2 ports at the computer´s rear side. Yet, this possibility is optional and not available as a function of all KVM devices.
Additional texts featuring more details
Additional support
If you cannot fix your problem with the help of these FAQs you can also contact our DIGITUS® support team via email. Please add in a note of your email a comment stating that the FAQs did not help you solve the problem.
If you send an email to us concerning problems with your KVM device, please give us information about the following aspects, for this will probably avoid additional queries and save you some time:
- Monitor (part number, manufacturer, if available hyper link to product page)
- Screen resolution of graphics cards you use (incl. refresh rate)
- Connected devices (mouse/keyboard (part number, manufacturer, if available hyper link to product page))
- Connection cables used between PCs and KVM (part number)
- Connection cables used between monitor and KVM
- Ports used by the system cable between the computer and the KVM device (on side of the computer): USB only, USB+PS2, PS2 only
Legal aspects
Please also take into account in what way our pieces of advice and recommendations have to be used!