Portable Data Terminals (PDT)

Portable Data Terminals (PDT) operate like “electronic clipboards” similar to what United Parcel Service (UPS) and Federal Express use. These terminal devices are used wherever portability is an issue. RF (Radio Frequency) terminals are used in applications where portability and real-time access with a host computer is necessary. This type of terminal is commonly used in warehouse environments for order picking, receiving, and shipping.

The portable bar code reader provides a convenient and efficient way of collecting a large amount of bar code data while moving about away from the computer. When data collection is finished, the PDT can be connected to a personal or host computer through an ordinary serial link for uploading data to be further processed by the computer.

Portable readers are ideal in situations where inventory applications can be performed off-line or batched. Portable readers are relatively inexpensive when compared to most RF products and are easily integrated into a user’s environment. Some portables readers can be easily programmed on the unit itself and generally take less than one hour to program from start to finish. Other units can be programmed using C/C++ and require several weeks of development time. Generally, warehouse applications require only the item number and quantity to be input for inventory applications and thus a PDT is ideal for most operations. Others add the warehouse number, aisle, bin, and shelf which is also supported by most manufacturers’ PDTs.

The data that is stored in the PDT can be uploaded into a host computer such as PC using the manufacturer’s communication protocol software package or an off-the-shelf program such as PROCOMM. The data is generally loaded into a text file using delimiters to separate the fields. Once the information is loaded into the computer, the data can be processed by any host application.

PDT Characteristics

PDTs normally include 128k (or 256k) of memory, a membrane keyboard, and a display. For most applications, 128k or 256k of memory is sufficient to store a complete day’s worth of work and should be uploaded no less than once a day in any case to minimize the risk of losing data as in the event of loss of primary power. Most PDTs are equipped with a real-time clock and date sequence to maintain a complete audit trail for the complete data collection process. When large, custom applications are required, some PDTs can be upgraded to support 256kB to 4MB of memory.

PDT keyboards come in various shapes and sizes. Keyboards can be numeric or alphanumeric, with or without assignable function keys. To maximize the size of the keys on the hand held unit, some manufacturers use shift keys to combine two values per key.

The LCD display also come in various sizes. Typically, the display will support a 4 X 20 or 8 x 20 line(s) by character(s) message. Some manufacturers support backlighting of the display to improve the readability.

Operating Systems and Programming Languages

PDTs generally have proprietary operating systems installed even though some manufacturers now support DOS or DOS like operating systems Ñprimarily to allow programmers to develop in languages such as BASIC, C, or PASCAL. At first glance, this may seem the best choice, but for most data collection applications this can be an overkill. Granted, the user must become familiar with the manufacturer’s programming language, however, this is usually not very difficult and can often be performed by a nontechnical individual. Proprietary operating systems are designed specifically for data collection applications and are generally quite efficient when it comes to developing bar code applications.

The other alternative is to program the hand held unit using a Resident Operating Program (ROP), if it is supported by the manufacturer. The ROP is built-in to the reader and allows the users to easily define the data fields, the number of fields, the width of each field, prompting messages, and record delimiters of a file. The ROP is ordinarily flexible enough to support most data collection applications.

Integrated vs. Non integrated Scanner

When considering purchasing a PDT, operation and handling should be a key component in the decision process. The size and weight of the PDT are also particularly important. Many of these PDTs are now smaller and lighter and even have pistol grips designed for specific warehouse applications. Several questions must be asked when deciding which PDT is required. Does the user need both hands to operate the reader? When scanning the bar code, will the user be able to physically touch the bar code or scan it from a distance? If so, how far away? In general, tethered scanners (nonintegrated) are several hundred dollars less than portable units with integrated scanners. In warehouse environments, laser scanners are usually recommended since “point-and-shoot” scanning is much faster than stripping a bar code and since the users will generally stand at a distance from the equipment.

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