What an interface does
A display interface carries signals between a computer and a display: video from the computer to the display, touch data from the display back to the computer, and sometimes audio or power as well, depending on the interface. A display that shows a picture but does not respond to touch has video without touch, while a display that responds to touch but shows no picture has touch without video, and both failures usually point to an interface problem, not to a display fault, because the display needs both signals to work fully.
Interfaces differ in what they carry, in their quality, and in their connectors, and a buyer who chooses a display should choose its interface set as carefully as its size, because a display with the wrong interface cannot be connected without an adapter, and an adapter adds cost and a point of failure. The model pages state the interfaces for each model, and the inquiry should confirm them.
VGA: analogue video, widely compatible
VGA carries analogue video from a computer to a display, and it has served displays for decades, which makes it widely compatible with older computers and with installations that already use VGA. Its analogue signal can lose quality over long cables, and it does not carry touch or audio, so a touch display over VGA still needs a USB connection for touch data, and a display that needs audio needs a separate audio connection, unless it has speakers fed by another channel.
VGA suits an installation where the computer has VGA output, where the cable run is short, and where touch is carried separately over USB, which is the arrangement on the monitors on this site. A buyer who uses VGA should check the cable length, because a long analogue cable will soften the picture, and should confirm the touch channel, because video alone does not give touch.
USB: touch data and sometimes power
USB carries touch data from a touch display back to the computer, so the computer knows where the screen was touched, and it also powers some small displays, though it does not power a large monitor on its own. A touch monitor that uses VGA plus USB therefore needs two cables: one for video, one for touch, and both must be connected for the monitor to work fully, because a monitor with video but no touch is a display without input, however good its picture is.
A buyer who connects only one cable will discover the missing function on arrival, and will waste time diagnosing a display fault that is actually a connection omission. Both cables must be connected, and the inquiry should confirm the cable set for the exact model, because cable sets differ by model, and a cable set that is assumed will not match a cable set that is delivered.
HDMI: digital video, as an OEM option
HDMI carries digital video, and often audio, over a single cable, and it is offered as an OEM option on the monitors on this site, rather than as the standard interface. Its digital signal holds its quality further than analogue VGA, and it suits a sharper display, but it does not by itself carry touch: a touch display over HDMI still needs a USB connection for touch data, unless its touch runs over another channel, and a buyer who assumes HDMI covers everything will leave touch unconnected.
A buyer who needs HDMI should name it explicitly in the inquiry, because the standard interface is VGA plus USB, and an HDMI model is a different configuration, not the same model with a different cable. The specification table on each monitor page states the interfaces for that model, and the inquiry should confirm them, including the touch channel, so the full interface set is known before ordering.
Choosing an interface set
Choose by the computer and the installation: VGA plus USB where the computer has VGA output and USB ports, HDMI where the computer has HDMI output and a sharper display is needed, and always confirm the touch channel, because video alone does not give touch. Check the cable lengths as well: analogue VGA loses quality over long cables, while digital HDMI holds its quality further, but both need cables that reach, and a cable that is too short cannot be stretched, while a cable that is too long for VGA will soften the picture.
A buyer who is unsure which interface their computer has should check the computer's outputs before ordering the monitor, because a monitor with the wrong interface cannot be connected without an adapter, and an adapter adds cost and a point of failure. The inquiry should name the computer's outputs, so the supplier can confirm the interface set for the exact model, rather than the buyer guessing.
Adapters and converters
Adapters and converters can bridge an interface mismatch, but they add cost, add a point of failure, and sometimes lose quality or function, especially for touch, which an adapter may not carry correctly. A buyer who needs an adapter should ask whether the display can be ordered with the right interface instead, because a native interface is always better than an adapted one, and a display ordered with the wrong interface and an adapter will cost more and work less well than one ordered with the right interface.
An adapter should be a last resort, not a plan: if the computer's outputs and the display's interfaces do not match, the better plan is usually to order the display with the matching interface, or to use a different computer output, rather than to adapt. The inquiry should name both the computer's outputs and the display's interfaces, so the supplier can confirm the match, or suggest the right configuration.
Cable planning
Cable planning should be part of display planning: the cables must reach, must be routed neatly, and must not be pulled, bent sharply, or crushed, because a damaged cable will fail intermittently before it fails completely, and an intermittent failure is harder to diagnose than a complete one. A buyer who plans cables with the display will install a display that works reliably, while one who does not will install a display that fails at its cables, however good the display itself is.
Cable lengths should be measured, not estimated, because a cable that is a little too short cannot be stretched, and a cable that is much too long will coil, snag, or look untidy. Measure the route, not the straight-line distance, because cables follow walls, desks, and brackets, not straight lines, and a route that is longer than expected will need a longer cable than the straight line suggests.
Before you order a display
Name the model, the size, the interface set you need, the quantity you have in mind, and the market you sell into, in the inquiry. Ask for the specification for the exact model, the minimum order quantity, the lead time with its meaning, the warranty terms, the payment and shipping terms, and the certificates that apply to your market, by name, with documents attached. Do not pay before these have been confirmed for the exact models in the order.
A display is only as good as its interface set, and the interface set is only as good as the confirmation. The interfaces guide page explains the interfaces in the same terms, and the model pages give the per-model interface specifications, so a buyer who follows both will rarely be surprised.
A note on sources and confirmation
The model specifications and trade terms referred to in this article come from the company profile's official product pages, as presented on this site's model and category pages. Trade terms are stated per model only: minimum order, supply ability and stock time differ by model across the official detail pages, and delivery EXW, though stated on all 101 pages, is still written per model rather than as a blanket promise, and stock time is not delivery time.
Figures that are not stated on a model page — a price, a payment, shipping or warranty term, or a certificate for a specific model and market — are confirmed per order in the inquiry, and this article does not invent them. Official list prices that appear on the official detail pages are transcription only and are never a quotation, and no certificate name, number, or issuer is stated anywhere on this site, because none are evidenced; certificates are available upon request.
Before ordering, name the model, the variants, the quantities, and the market you sell into, in the inquiry. Ask for the specification for the exact model, the minimum order quantity, the lead time with its meaning, the payment and shipping terms, the warranty terms, and the certificates that apply to your market, by name, with documents attached. Do not pay before these have been confirmed for the exact models in the order, because payment removes the leverage to resolve an unconfirmed item, and a confirmed order is the only basis for a safe purchase.