Green screen
By Alejandro Calero, General Manager, Mobilis | February 27, 2024

The Truth About Connectivity in the Warehouse: Green-Screen Apps

What is it about telnet that makes it possible for modern warehouse devices to continue to run it?

Telnet is a technology term that takes us to times before the internet era itself. In the 1980s, a techno-thriller movie called “War Games” showed us how a teenager almost started World War 3 by hacking into a U.S. Department of Defense’s server while trying to patch his grades through a telnet connection. In 1999, another sci-fi movie showed us how Neo, the Chosen One, perceived the true nature of “The Matrix”: tons of data, displayed in green text, transmitted in lightning-fast speeds on a black screen.

Now, in 2024, it is estimated that 60% of all mobile devices currently in use in distribution centers around the world run green-screen applications to connect to warehouse management systems (WMS) or other enterprise applications, such as IBM’s AS400.

Why? What is it about telnet that keeps it so relevant technology 50 years after it was invented?

Hollywood movies provide good hints: Telnet allows for connectivity to remote applications, and it is super-fast. But there is more to telnet than remote connectivity and speed. Before you consider migrating from a telnet-based application to something else, make sure you don’t lose any of the advantages that Smart Telnet (TE) clients offer today:


In times when most of the WMS vendors are providing Software as a Service (SaaS), mobile devices require secure connections to the cloud environments where the SaaS applications are hosted. Smart TE clients meet this requirement by providing SSH encryption.

Session Persistence

Dropped sessions are the number one productivity killer in warehouses around the world. Internet latency, roaming between antennas, entering wireless dark zones, or having the battery die in the middle of the shift may interrupt a session, forcing workers to reenter their credentials and then search and navigate to the task where the session was dropped. This interruption takes anywhere between one to three minutes to recover per incident. Consider this example: If one order takes 10 minutes to complete, one dropped session degrades the worker’s fulfillment productivity by up to 30%. Real-world negative impact levels are closer to 10%, but that’s still very high.

When an interruption occurs, Smart TE apps make the session persist, meaning that the screen appears to freeze momentarily, but then recovers, allowing the user to continue to work on the same screen where the interruption occurred. No time is wasted reentering credentials or searching for the order that was in progress. This feature is called “session persistence.”


Warehouse workers use their mobile devices to keep track of inventory as it traverses the various stages of storage, from receiving down to delivery. While capturing the movement of inventory is important, physically moving the inventory is the workers’ ultimate goal. Therefore, mobile devices must provide instructions to each worker in as succinct a format as possible. There’s no time to waste. Activity is fast paced. Instructions on the screen must be clear and short. The faster the screen transitions from one to the next, the more inventory the worker will be able to move throughout the day. A TE interface meets these requirements by presenting the instructions in clear, short, plain text. The screen’s transition response time is instantaneous.

Easy Integration with New Technologies in Your Warehouse

Integrating a host of new technologies may boost your warehouse team’s overall productivity. For example, wearable devices allow workers to keep hands free for moving inventory, which helps increase both output and safety in the workplace. That’s why we’re seeing such rapid adoption of wearables in these environments right now. Fortunately for you, there are Smart TE clients ready to integrate these new wearable devices, saving you the time and cost that would otherwise be required to upgrade the entire WMS application if you didn’t have this easy way to make your WMS work with your new wearables. Consider Zebra’s WT6000 mobile computers. A Smart TE client will automatically convert one long vertical screen into two halved screens, taking full advantage of the WT’s horizontal screen. Another exciting wearable device is the heads-up display (HUD). A Smart TE client will allow you to pick the significant information on a TE screen – a product’s location, for instance – and present it on the Zebra smart-glass display without having to write one single line of new code.

The same is true for integrating autonomous mobile robots (AMRs). One member of Zebra’s Independent Software Vendor (ISV) program has eliminated the need for upgrading the WMS to make them compatible with Zebra’s Fetch robots.

Less sophisticated technologies, such as bidimensional barcodes, are even easier to integrate into warehouse workflows. Consider the case of a 3PL company in Mexico that uses 2D barcodes at its receiving gates. By scanning each pallet one time only, its Smart TE app automatically populates all fields across multiple screens, such as date of manufacture, quantity, and SKU codes, reducing the 3PL’s receiving time by 30%.

Multi-modal Data Capture

Adding voice to a Smart TE app is one of my favorite use cases. A Smart TE client that allows voice as another mode of data capture saves a ton of money for companies seeking to adopt voice-picking technology in their operations. A voice-enabled TE client reuses the entire warehouse technology infrastructure: the barcode-reading Android devices, the WMS workflows, and equally important, the workers’ expertise. You will not be forced to eliminate the barcode-reading steps that you deem indispensable to your operation, hence the multimodal nature of the data-capturing. Each worker will simply speak out the instructions and data that they were previously punching into the keyboard. The Smart TE app will convert such voice commands into the same old keyboard presses that the WMS expects. The information on the screen will be read out loud to the worker, eliminating the need to hold the device in front of their face. It’s a truly liberating experience, enabling hands-free, eyes-up operations, without the need to add duplicating voice-only servers and devices.

In Other Words…

If you run your warehouse on a TE-based WMS, congratulations, you are in good hands. My guess, though, is that you’re not taking full advantage of your existing investment. So, before considering any expensive automation initiative in your warehouse, my personal advice is that you get more out of your existing Zebra devices and Smart TE software.

To learn more about Zebra’s ISVs that provide Smart TE, go to Zebra’s Partner Locator here.


About the Author

Alejandro Calero is an industry veteran who has provided terminal emulation software-related services and professional advice to corporate customers, hardware manufacturers, WMS vendors, and the partner community throughout Latin America for the past 20 years. He runs Mobilis, a consulting company in Mexico City, which specializes in Smart TE applications, such as voice-enablement and lean warehousing applied to WMS mobile workflows. Mobilis is a member of the Zebra Independent Software Vendor program. Connect with him on LinkedIn.

Blog, Article, Warehouse and Distribution, Digitizing Workflows, Handheld Mobile Computers, Wearables, Software Tools,

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