Switching And Routing Hdmi For Training And Demo Rooms

There are many instances where one requires a system with the following specification. Drive a number of displays with touch screens on a one-to-one basis where each screen is connected via DVI or HDMI to a Mac or PC. Then, allow an instructor or demonstrator to be able to select a master mode such that their master PC then provides the display content which is routed to all of the displays. Examples of this are common for Training and demo rooms, visitor centres and museums, schools and universities.

It is often best to locate the students PCs (when I mention PC please understand that this equally applies to Mac and other computing platforms) away from the actual display device. The PCs can be installed in a cabinet or rack away from the main area. This has the advantage that the students cannot interfere with the switches on the PC and also it makes the demo room or training environment more of a clean and tidy space. This solution means routing the audio, video (and in case of touchscreen or mouse) and pointing mechanism between the output display device and the source PC. One solution is to use longer cables but most VGA/DVI and HDMI cables have stringent restrictions on the overall length available. Longer cables (typically over 5m) will result in a lower resolution being available on the display. To overcome this Fibre optic HDMI extension cables, DVI fibre extender cables can be used to supply the video content and USB can be transmitted also over USB Fibre extenders.

Extending DVI , HDMI and other video signals using a fibre optic cable has several advantages particularly where installed in a hospital or security minded environment (police, security services, courts, local government, MoD etc). The fibre emits no electrical radiation and is also immune to electrical noise which ensures reliability of transmission. The fibre also provides total electrical isolation between source and display. The fibre extenders employ multi-mode fibres to transmit the DVI and/or HDMI signals and some devices are also capable of transmitting audio, RS232 and other signals.

For a HDMI input monitor the audio is transmitted synchronised with the video steam whereas DVI is a video only signal and audio will need to be multiplexed onto another signal for transmission. A DVI+Audio fibre extension box is available which will take DVI and audio and provide transmission of this combined signal up to 2Km.

So far we have a system where students' displays are connected on a one-to-one basis back to a computer. The next feature to add is to enable an instructor to take over the student displays and for a master computer to provide the display content. HDMI and DVI switch boxes and matrix routers exist for switching HDMI and DVI signals from one or more input to one or more output. Distribution boxes provide a digital copy of a HDMI or DVI signal for distributing to multiple monitors, all in sync. The instructors' master computer can be connected to a DVI or HDMI distribution box to provide the same number of outputs are there are screens. A HDMI or DVI switch box then provides switching between the two source inputs such that the students display either shows output from their PC or from the instructors PC. The touchscreen inputs from the students monitors are not connected back to the master PC so only the instructor can use a point device.

By using a HDMI based system, the audio is dealt with at the same time as the video signals. The HDMI switch box or matrix switch routes the audio along with the HDMI video signal. PCs and Macs don't all have a HDMI output available so for this reason a DVI + audio to HDMI converter box.

In conclusion, the ability to drive full HD resolutions in training and demo facilities is now with us and can be combined with the latest HDMI and DVI switching products to create some very attractive solutions. The use of fibre extenders as an alternative to long cables or Cat5 based systems is starting to find traction especially in areas where security or safety are an issue.

By: Chris Cowper

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