Mobile Technology Basics

Mobile terminals or "Portable Data Terminals (PDTs)" are used to bring the barcode reader to the barcode. For instance, in a grocery store environment, the customer brings the barcode to the scanner. However, when the time comes to do a monthly or quarterly inventory, it just won't make a lot of sense to bring the products to the front of the store. That's where PDTs come into play. There are a variety of options, including point-of-sale scanners, numeric keypads, alphanumeric keypads, character displays and graphical displays. The following information should help you match the proper PDT to your customer's needs.

A Portable Data Collector is made up of the following components. Selecting the proper one can mean the difference between a life-long customer and a one-time customer.

  • Scanner
  • Display
  • Keypad
  • Interface
  • Memory
  • Accessories
  • Application Development


Do you even need to read barcodes? For example, someone who reads meters for the electric company has no need to read a barcode. He just needs to key in some data.


The best way to begin is by understanding the customer's application. Some PDTs have a scanner built into them. This "integrated" scanner might come in different models, such as standard range, long range and high visibility (see Scanner Assist for more on scan engines). If the PDT's integrated scanner will read 100% of your customer's barcodes 100% of the time, then it may make sense to go with an integrated scanner. The scanners on some PDTs can twist to accommodate right-handed or left-handed users.


Remember playing tether ball as a kid? The ball was "tethered" to the pole with a rope. Tethered PDTs are similar. For example, your customer might fall in love with a PDT that you've recommended, but this particular PDT only has a standard range integrated scanner and they need a long-range scanner. This is when you need to tether a long-range scanner to the PDT. The scanner will then be able to read barcodes from 20 feet, and the decoder built into the PDT will decode the barcode. Of course, this would only work on those PDTs that have an external scanner port.



Some customers simply need to collect the item, quantity, and location during a cyclical inventory. They would require character-based PDTs.

Graphically based

A graphically (or pen-) based PDT is used when a customer needs a Windows-like application. For example, a cola delivery person at the grocery store could select the store from a drop-down menu, select the item from a drop-down menu, and then identify a quantity. All of this could be done with a pen-based terminal. This type of terminal is also very useful for police officers who are on site reconstructing an automobile accident. Rather than drawing the facts on a piece of paper, they could use a pen-based terminal.


There may be times when your customers need to display character-based information but also need to collect a signature. This is when a "hybrid" PDT comes into play. You don't have to worry about having to program a Windows-based terminal, but you still can capture a signature.


As always, make sure that you match the terminal to your customer's needs. If your customer is doing an inventory and only collects the item and quantity, then they need a character-based PDT with a numeric-only keypad. However, if they also are collecting location information, and their locations include letters, then they need an alphanumeric keypad. Don't stop there, though. Are the users wearing gloves? If so, the size of the keys makes a difference. Always be aware of:

  • Who is using the PDT?
  • What type of information they are collecting?


Ask these questions:
  • How will your customers get the application onto the PDT?
  • How will they get the data off the PDT?


Some PDTs have an RS-232 port on the bottom of them. It may be a DE-9 connector or a RJ connector. Either way, it uses serial communications for getting data to and from the PDT.


You need to have some means of getting data to and from PDTs that have no physical ports on the outside of them. These PDTs literally use lights to exchange data. As you know, meter readers also work on rainy days, so they need a PDT that is designed to continue operating while exposed to dust and splashing water. That's when you'll hear someone talk about needing a device with an "IP54 rating."


IrDA (the Infrared Data Association) is another means of sharing data between two IrDA-compliant devices. For example, a PDT and a printer might have an IrDA port on them. This would allow the user of the PDT to point the IrDA port on the PDT toward the IrDA port on the printer to begin printing. No cabling is required. However, one downside to IrDA is that it requires a clear line of sight. Unless the two devices are looking directly at each other at a close proximity, the "receiver" (printer) will not "see" the "transmitter" (PDT).


Read-Only Memory (ROM)

On a PDT, this is where device settings (similar to BIOS on a PC) are stored. This also is where the manufacturer stores information necessary for starting up the terminal and storing an application on it. This area is only accessible by the manufacturer.

Non-Volatile Memory (NVM)

Also called "NVRAM," this is where the application is usually stored. Power is not required for its existence, so in that sense, it is not volatile.

Random Access Memory (RAM)

Just like on a PC, this is where applications go to play. The application is copied from NVM to RAM and it runs from there. Operating system commands, drivers, and other frequently accessed information are also stored in RAM. This simply maximizes the speed of the application. When power is lost, so is all the information stored in RAM.


Static Random Access Memory (SRAM) is typically used for the storage of "look-up" files and sometimes for the storage of applications where there's not enough NVM to store the application (or it's just the programmer's preference to have it stored on an SRAM card). It's like a hard drive, but it is "battery-backed." As long as the battery is good, so is the data. If the battery dies, so does the data. (Back to our example of the meter reader: Wouldn't it be nice if the PDT would automatically display the address of the current customer and his next customer and tell him where the meter is on the house? All that information could be stored in a file that was downloaded to the PDT. The application on the PDT would "look up" that information and display if for him.)


"Flash is like a floppy." Remember that. Flash is functionally the same as SRAM but does not need a battery to maintain the data stored on it and is slower than SRAM.


Communications Dock

A communications dock is recommended if your customer is using a PDT on a daily basis. It's not practical to expect the customer to plug a communications cable into the bottom of the unit every time he wants to upload the data to the host. This is where the cradle comes in. It's also a handy place to store the PDT and to charge the battery. Further, a cradle is required for PDTs with an optical interface.



Use it until it dies, then dispose of it in accordance with local ordinances. We're talking your typical 9V and "AA" battery here.

Nickel Cadmium (NiCd):

NiCd batteries are the first generation of rechargeable batteries. You can use it until it dies, recharge it, and go back to work. The problem with NiCd batteries is what is commonly referred to as the "memory effect." If a battery is used for the same amount of time between recharges, it will soon only allow the battery to be charged to that amount. For example, if you use a battery for four hours every day before recharging, that battery will soon develop a memory and only allow four hours of use. Proper battery maintenance is of supreme importance with NiCd batteries. Do not re-charge them until they have been totally drained.

Nickel Metal Hydried (NiMH):

NiMH batteries are the next generation in the world of re-chargeable batteries. These batteries have no "memory effect" and tend to have a longer life than NiCd batteries but are more expensive than NiCd.

Lithium Ion (LIo):

LIo batteries are rechargeable, have no memory effect, have a longer life than NiMH, and are more expensive than NiMH batteries.

Battery charger:

If you can charge the battery while the battery is in the PDT, then why would you need a battery charger? Because the PDT might need to be used on more than one shift a day. Also, what if the battery dies? For this reason, we always recommend at least two batteries per PDT. Some cradles can charge an additional battery, so an additional charger may not be required. Otherwise, there are single and multi-slot chargers.


A holster holds the PDT so that you can use both hands. Of course, a holster would not be able to also hold a tethered scanner.


Some PDTs have the ability to be connected to a portable printer. This would be very helpful for someone that needs to re-print shelf labels at a store. Every portable thermal printer has a unique programming language, so it won't be a "plug and play" solution. Typically, printing is done either through the serial port or the IrDA port.

Application Development

PDTs generally are not devices that you take out of the box and go to work with. An application must be written to run on the PDT, and you must also be able to make use of the collected data at the host end.

Operating Systems:

Be aware that different PDTs can have different operating systems. Some have one version of DOS, while others have a different version of DOS. Some might have Windows and some might have Windows CE. Operating systems may vary from PDT to PDT.

Application Development Kit (ADK):

If you need to get to the fullest potential of the terminal, then the ADK is for you. But you may have to spend a lot of time writing your application.

Rapid Application Development (RAD) Software:

Rapid Application Development tools provide a Graphical User Interface (GUI) that allows for the rapid development of applications for your customer. These are not designed to give you the ability to write robust applications that you could with an ADK. However, it should give you everything you need to meet the needs of a large portion of your customers. They are time-savers, but not for people with any programming experience.

Matching a PDT to an application:

When matching a PDT to a customer's application, be sure to listen to the needs of your customer. There may be things that your customer is not aware of that would help make his/her employees more productive. This is where you add value to the deal. By understanding the capabilities and limitations of using mobile terminals, you may be able to determine whether your customer actually needs a wireless or mobile solution (see Wireless Assist). If you don't have the expertise to write an application, contact ScanSource Technical Support.