Digital signage is everywhere, from boutique kiosks to highway billboards. HD video streams have replaced static displays. Very large screens are the norm, and sensors are changing the way audiences interact with these signs.

Conventional HDTVs and computer displays have become larger and more interactive. Tablets and smart phones bring us the joys of multitouch, which now can be found in many digital signage solutions too. Video cameras can monitor audience reactions to these signs, which will respond accordingly, as well.

While its hardware and software looks a lot like the technologies behind conventional HDTVs and PC displays, digital signage is significantly different because of its requirements. Displays often are outdoors or in high-traffic areas that require rugged devices. These displays are subjected to drop tests and other trials before they’re released (Fig. 1). Thicker, stronger glass isn’t always the answer because of sensor and parallax issues.


1. Digital signage needs to stand up to rough treatment, which is why displays typically need to pass a range of tests like dropping a steel ball bearing on them.

Rugged aspects of digital signage design are just the start. Systems also often need to operate in full sunlight or in the dark. Glare is easy to solve for handheld devices, but it’s a challenge with a fixed position and a display a that’s couple meters wide.

Likewise, capacitive multitouch is popular for tablets and smart phones, and it’s available for many digital signage products. Unfortunately, it doesn’t work as well in all environments or applications. There are many interactive alternatives, though, from resistive touch to ultrasonics to infrared solutions.

More options are in development or on the market. E Ink’s ePaper technology can be deployed in large, flexible sheets that exceed the size of even the largest LCDs. Color versions are now available (see “Color Comes To E-Books”). Emerging practical autostereoscopic 3D displays are more effective for handheld devices, but events like the International CES have highlighted large HDTV-size versions.

Digital signage solutions have a lot in common with smart TVs and all-in-one PCs. They all have a processing system behind a display and usually some form of interaction with their users. Most also have some level of connectivity, although digital signage applications may have transient or low-speed links while consumer devices typically push the performance envelope.

Digital signage applications are normally fixed, but they can be large and small. Keep an eye out for in-store marketing and pricing displays. Some only show a price and possibly a description or code, but these devices may do much more. They normally have a wireless network connection so pricing can be changed automatically, opening opportunities for everything from real-time inventory to user interaction.

Scenarios range from real-time electronic coupon generation to targeted advertising. Interaction also can account for other sensors and wireless technology as well as the Internet.

Quick response (QR) code could be displayed and scanned using a smart phone with an app that communicates with a service matching the phone with that particular in-store display. From there the options become boundless, such as allowing customers to check the inventory of nearby stores if the desired product isn’t available on site. These systems also might initiate a video call to talk to a sales or service representative.

QR codes are just one example of how user interaction could work. Then there’s the Bump Technologies solution, which uses the accelerometers inside a phone along with an Internet link to determine when two phones, or in this case a phone and a digital signage display, are bumped together. Bump uses time and accelerometer details to determine the two items being linked.

Near field communications (NFC) is showing up in phones for electronic payment applications, but it also could be used in digital signage. Likewise, Bluetooth and Wi-Fi could be used. Even voice interaction is an option. It all depends upon the application, costs, and benefits. Of course, it all starts with the display.

Display Signage Technology

Digital signage that matches large-screen HDTVs tend to be the most noticeable, but they are only part of the mix. Those 12-in. LCDs in the checkout line at the store playing advertisements fit into the same category as the interactive kiosks found everywhere. Advantech’s IDK-2108 is a typical ultra-high-brightness industrial display with LED backlighting designed for embedded outdoor applications (Fig. 2).


2. Advantech’s IDK-2108 is an ultra-high-brightness industrial display with LED backlighting.

LCD screens tend to dominate, though some applications use plasma and projection systems. Other display technologies like ePaper also bring their features to the application category. For example, ePaper does well in full sunlight and uses very little power. It would be ideal for a digital signage applications where power is limited, such as hiking trail signposts.

Other display technologies come into play for specialized applications. Stratacache’s PrimaSee translucent digital display can show high-definition, full-motion videos. It’s the same kind of technology used for transparent displays often seen on TV or in movies to provide a high-tech feel that “old” flat-panel displays lack. It can be used on freezer or cooler doors and other glass retail fixtures.

The rugged design aspects are key, though. An HDTV typically operates three hours per day, while a digital signage application runs an average of 16 hours per day. Digital signage systems are often in place for at least five years, too. Some run for decades.

Displays in this market typically have three- to five-year warranties and a rated life on the order of 50,000 hours. In-field service needs to be minimized if not eliminated because of the cost. Just rolling a service truck can cost at much as $1000. That’s one reason networking is so important from a software upgrade standpoint.

VESA’s (Video Electronics Standards Association) VGA and DVI interfaces are giving way to HDMI (High Definition Module Interface) and VESA DisplayPort. The bandwidths and functionality are higher, and the cabling is smaller. DisplayPort’s support for multiple, daisy-chained displays is more important in some areas. Allowing the processing system to drive more than one display at a time is handy for synchronized displays that are often deployed in closely spaced arrays.

There are even more options for multiple displays because of networking and the low cost and small size of the processing platforms. PCs used to be the same size as some displays. Now, a system might be the size of a credit card and drive a 55-in. display.

Although not representative of digital signage platforms, the $25 RaspberryPi can plug into an HDMI display (see “Hot RaspberryPi”). Its 700-MHz ARM11 doesn’t use a heatsink. Comparable rugged alternatives are more costly, but that is still a small fraction of the digital signage system.

VGA, DVI, HDMI, and DisplayPort specify external display connections. Internally, low-voltage differential signalling (LVDS) has dominated. Embedded DisplayPort (eDP) and internal DisplayPort (iDP), though, look to make inroads to direct internal connections.

WinSystems’ Panel PC is a typical digital signage display system (Fig. 3). It has a rugged PC mounted on the back of an industrial display with a resistive touch display. The motherboard can run a 1.8-GHz Pentium M. It also has PC/104 expansion, although the standard peripheral complement will normally suffice, including Ethernet, Wi-Fi via a MiniPCI socket, and space for a hard drive. The newer PPC65 family’s front bezel is environmentally sealed to meet NEMA 4/IP65 requirements (see “IP65-Rated Touchscreen Panel PC Handles Rugged Environments”). It runs a 1.6-GHz Intel Atom as well.


3. WinSystems’ Panel PC hides a Pentium M motherboard behind an industrial-grade LCD. It has PC/104 expansion support.

These systems are all conduction cooled, which is the norm for digital in signage applications. It tends to limit computational capabilities, but even GPUs can run on conduction cooled systems. In addition, most digital signage applications are less aggressive in performance. The heavy lifting is in HD rendering, which a GPU often handles. On the other hand, gaming and gambling applications are pushing performance to deliver more immersive experiences.

Internal or form-fitting processing systems are one approach to digital signage. Another is to take advantage of the VESA standard mounting holes found on the back of most displays, including many off-the-shelf HDTVs. These holes often are used for attaching the display to arms or wall mounts. They also can be used to mount the processing support.

VIA Technologies’ AMOS-5002 has VESA mounting holes on its back so it can fit between a display panel and a VESA-compatible mount (Fig. 4). The case holds an EITX-3002 motherboard that runs the dual-core VIA Nano X2 E-Series processors.


4. VIA Technologies’ AMOS-5002 contains an EITX-3002 motherboard. The motherboard runs a dual-core VIA Nano X2 E-Series processor.

The board’s peripheral connectors on both sides expose more interfaces while simplifying cabling. Many digital signage applications are display only, but many interact with other devices as part of a large embedded system. The AMOS-5002 fits best in this type of application environment.

MEN Mikro’s G214 is a 3U CompactPCI Serial multi-display board (see “Embedded PCI Express Still Emerging”) has four DisplayPort 1.2 interfaces (Fig. 5). A wider front panel offers two additional DisplayPort interfaces. It runs AMD’s 600-MHz Radeon E6760 GPU. A standard CompactPCI Serial backplane would allow a CompactPCI Serial host to control seven G214 boards for a total of 28 displays, which all could be tied together to form a single large logical display.


5. MEN Mikro’s 3U CompactPCI Serial G214 multi-display board has four DisplayPort 1.2 interfaces that are driven by AMD’s 600-MHz Radeon E6760 GPU.

Incorporating the processing module on the back of the display or in a separate system like the one that a G214 board would be included in is one way to approach digital signage applications. This is less of an issue for kiosks where there might be more space for the processor, but it also can suit wall-mount systems. Digital signage displays usually aren’t as thin as the ultra-thin HDTVs, though they can be only a couple inches thick.

Putting the modules inside the display is much more manageable now. Compact modules have the performance and connectivity necessary for most applications. Systems with the processing module built in are common but typically lack standards. Some companies have come up with their own internal or removable module standards within their project lines.

The Open Pluggable Specification (OPS), which Intel supports, has received lukewarm support elsewhere. The modules are designed for larger displays, and products are available from third parties. The systems normally slide into the side of the displays like NEC Display Solutions’ N8000 series and are held in with two bolts. OPS provides enough space for a 2.5-in. hard drive within a 200- by 119- by 30-mm case.

Interactive Digital Signage

Getting neat stuff up on screen can be a challenge, but making it interactive is even harder. Still, interactive screens are becoming more common because of the increased use of all types of sensors.

The interactive digital signage (IDS) systems from Elo TouchSystems/TE Connectivity employ surface acoustic wave (SAW) or optical touch sensing interfaces that place the sensing system in the bezel around the display panel, unlike resistive and capacitive touch systems, which are on top of the display (Fig. 6). Optical touch sensing uses many different approaches.


6. Elo TouchSystems’ IDS displays employ surface acoustic wave or optical touch sensing interfaces.

For example, the Barnes and Noble Nook Simple Touch e-reader uses IR emitters and sensors spaced around the display periphery. Optical sensing systems sometimes employ cameras looking across the surface to detect touches. The number of components, accuracy of the system, and multitouch support all come into play when choosing these systems.

Designers need to consider the type of touch interaction to support. For instance, capacitive systems are usually restricted to displays under 46 in., and they don’t handle fingers inside a glove very well. Likewise, all systems support single touch, but multitouch support and accuracy vary widely depending upon technology and implementation.

The dominant operating system platform depends upon the kinds of digital signage being considered. Microsoft Windows is popular in larger displays where PC platforms are common and networks connect the platforms to Windows-based servers or control systems. Windows multitouch and table device support has helped in interactive designs because touch interfaces typically are supported and connected via USB.

Linux, the other major player, is more dominant in more embedded application areas such as kiosks. Android is becoming important, as embedded Android support is more available.

Sensor Aware Signage

These days, the availability of touch and display drivers is not the issue. It’s all the other sensors that are coming into play. GPS comes in handy if the sign is on the move, like on taxicabs. But most digital signage applications are less mobile. Sensors such as proximity sensors and video cameras are more likely options.

Cameras are becoming more common on smart HDTVs and digital signage hardware. They can be used to detect an audience and provide interaction feedback to applications running on the display. Basic surveillance is another potential use.

Resolution, speed, and other characteristics will dictate the kinds of feedback that cameras can provide. Low-resolution cameras can perform basic object and movement recognition, which is useful if an application simply needs to know if there is an audience or how large it might be. Face position identification and face recognition require higher-definition cameras.

Microsoft’s Kinect or similar technology may wind up on top of digital signage to provide 3D feedback. Gaming is one potential use, but the technology more likely would be used to augment or replace a touch interface. For example, the audience may be asked to point to the items or locations on the screen that are of interest.

Video processing is a heavy computational chore that could be challenging for unaccelerated fanless hardware, especially if additional functionality such as gesture recognition is added to the mix. A network connection could offload these chores to a remote site. Also, hardware acceleration could be incorporated either in the processing module or the peripheral. The Kinect uses a custom, low-power system-on-a-chip (SoC) to handle its infrared sensor and video camera.

Lighting around a display can be a help or a hindrance depending on the technology employed and the desired mode of operation. A camera looking into the setting sun probably won’t get a very good picture of the audience. Likewise, the Kinect’s infrared projection would be useless in full sunlight. On the other hand, it would probably work very well indoors and may even work in low-light environments.

Digital signage applications often have other peripherals for interacting with users in addition to position and imaging sensors. RFID and barcode readers may be low-tech, but they’re very reliable. They can interact with a range of items from a convention attendee’s badge to a UPC code on a product someone wants more information about.

People also can use NFC, which is finding its way into smart phones, to interact with digital signage applications. NFC doesn’t have to be used only for financial transactions. It could provide information or authentication that would adjust the presentation or options available on screen.

Sensor-aware signage is cutting edge, but it may provide significant mainstream advantages in the future. It could be used to provide a better audience experience as well as more information to the application such as what areas on the screen look more interesting to the audience.

Signage Software

The software that runs on a digital signage platform has a number of chores, and these days it rarely runs in isolation. Often the devices are connected to a common store network requiring the software to be approved to operate on these secure networks. Remote management, content delivery, and audience feedback are just some of the other chores a system might be required to handle in addition to putting something up on the screen.

Part of the challenge for software developers is the wide range of applications that digital signage addresses. This is why most digital signage software vendors target one or more application areas.

Companies like Scala, Stratacache, and Four Winds Interactive provide software frameworks including the software that runs on the sign as well the management software that runs on a server. The coordinated distribution and display of information is a challenge considering the variety of displays that may be part of a system.

It’s one thing to handle half a dozen identical displays showing the same information over and over again. However, it’s quite another to manage hundreds of platforms that include a dozen different display types with different capabilities running a host of applications.

For example, a hotel that handles conventions may have more than just a schedule of events on display. IDS could provide maps, visual paging, and emergency messaging. It could even turn a display into a virtual concierge that could handle reservations immediately. Or, do you want to buy a featured app for your smart phone or tablet? The system can sell it to you too. It might be as easy as scanning a QR code on display.

The software frameworks provided by digital signage software vendors often include a range of servers and services. Content and ad management tend to be common services provided.

A player-style application runs on the display platform. A design tool is normally provided to create layouts, presentations, and applications to run on the display platform. Most platforms utilize custom presentation applications, although browser-based solutions can simplify presentation design.

Some platforms support Adobe Flash presentations. HTML5 is likely to play a more major part given its standards approach to content presentation including video and 3D graphics (see “What’s The Difference Between HTML4 And HTML5”).

The overall network management tool coordinates the distribution of applications and connects them to the content and ad management servers. More complicated systems may require integration with third-party servers or enterprise services.

A range of services can be used to augment the player applications depending upon the vendor. For instance, it’s sometimes useful to display the current weather report on a display. The display doesn’t need a GPS unless it’s mobile. Developers can usually select the details to be displayed and how they are displayed.

Network communication varies greatly depending upon the application, network, and software infrastructure. Many applications including IDS with HD video often rely on limited network interaction using the connection to download most of the software and content for local playback. This asynchronous approach enables the display to be useful even if the network connection is not available or if it is being utilized for other purposes.

Security crops up for a variety of reasons, including management of the digital signage environment as well as the system’s relationship to the network for the rest of the environment. For example, a store network that handles point-of-sale (POS) systems would need to handle financial information. If the digital signage devices are connected to this network, then it may have to meet the same level of security as the POS systems.

Displays typically are located in public areas. Access to the wired network may be difficult. Still, even a USB port on a display, possibly for a peripheral device like a scanner, could be a point of attack.

The frameworks, remote management, and software infrastructure tend to be vendor-specific with very little commonality except for the underlying operating systems and network communication.

Remote management tends to be customized and included as part of a “complete solution.” Network management standards like SNMP and IPMI are known in digital signage circles, but they usually aren’t part of the mix because they’re often seen as self contained.

Digital Signage And The Cloud

The cloud may make standardization or at least some commonality more prevalent as more companies outside of the usual digital signage market try to take advantage of its displays and sensors. This could be driven by the desire to integrate digital signage with other applications such as Smart Grid power management, HVAC support, and security.

Lighting and HVAC adjustments for areas within a hotel or convention center may be based on the movement of people into or out of those areas. They may be directed there via digital signage and surveillance, possibly at a low level to determine when a hallway or room is occupied, or they could be handled by sensors that are part of the digital signage system.

Wind River provides operating systems and tools to embedded developers including those working on digital signage applications. Digi International provides wired and wireless devices and services including iDigi, a cloud-based framework for working with these devices (see “How To Link Smart Energy ZigBee Devices To The Cloud”). Wind River and Digi have partnered to bring iDigi to more users including those working with digital signage applications.

Eurotech is another company delivering embedded hardware and software solutions. Its Everyware Embedded Software Framework provides services similar to iDigi (see “The Embedded Cloud Runs Java”). It runs Java and provides integration with enterprise platforms.

Everyware and iDigi are coming at the digital signage market from a much different perspective than more conventional IDS vendors. There is likely to be more competition and cooperation as applications areas merge or require more interaction like some of the scenarios described earlier.

Digital signage covers a lot of ground, and even the high end of the market is very specialized and fragmented. In many ways, it matches the typical embedded development environment that addresses a wide range of applications and tailors solutions to a specific instance.

Developers of closed systems rarely want to open them, but digital signage is becoming much more than a way to put up pretty pictures. It’s an important asset that needs to be exploited beyond its original arena, and that change is coming on all fronts.