On-line vs. Off-line
PDTs can access and update host databases in real-time using Radio Frequency Data Communication (RFDC) or off-line by batch processing at the end of data collection. In most cases, batch processing is chosen over RFDC mainly because of the cost differential. Historically, this has been the case, however, new technology and open connectivity solutions now exist to where RFDC can easily be implemented with most host computers. When deciding between an RF and batch system, cost should not only be the deciding factor. Both systems do have their own benefits and will improve inventory accuracies.
At a closer look, the risk of losing data is greater with off-line systems than with RFDC systems. With most off-line systems, users generally transfer data once or twice a day mainly for two reasons (1) to avoid the inefficiency of frequent trips to the batch station used to upload and download data and (2) to save off the collected data in the event of a hardware failure. If a hardware failure were to occur with the PDT, all the data stored would be lost.
If the end goal is to customize the PDT program such as simulating access to the host database, programming cost can be higher for off-line systems, simply because many computer departments don't have developers that can program in languages such as C, BASIC, or PASCAL. Most batch PDTs have Resident Operating Programs (ROP) that are built-in to the reader and allow 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. This is generally the reason why most companies purchase these batch units besides cost and development cycles.
RFDC access to a host database can substantially reduce unexpected stock outages. Since the data is centrally stored and accessed in real-time, an accurate count of the inventory level can be determined instantly. In addition, discrepancies can be reported immediately by providing "at the point" data entry and on-line validation. When using off-line systems, the benefits of real-time data entry and on-line validation can be simulated, but this is usually not practical since a good part of the time would be spent walking back-and-forth to record information in pseudo "real-time".
RF terminals have drastically come down in price. Some manufacturers even allow users to upgrade PDTs to radio frequency PDTs simply by adding (attaching) a modular RF transmitter to the terminal. Traditionally, RF terminals have been designed to emulate common terminal protocols, and thus a host modification is required to program RF applications. Some manufacturers allow access to host computers using development packages such as Microsoft's Visual Basic or Visual C/C++. Not only is the development cycle shortened when using Visual Basic for new applications, but the benefits of implementing RFDC systems is considerably less in price since proprietary hardware is no longer required and access is through a common PC. Application software can even be purchased to provide connectivity from the host to the RF terminal.