Retail POS terminals at sales counters such as those in banks and grocery stores are essentially a PC in a custom case attached to printers, scanners and displays.
Some of the peripherals are integrated into the POS terminal, such as the keyboard, cash drawer, simple pole display and receipt printer. Others are external to the terminal such as scales, large flat panel pole displays, credit card readers, and bar code scanners. All these external peripherals could be easily integrated via a USB hub and a single USB port on the POS terminal. However, as these devices have traditionally been designed for the RS-232 interface, switching to USB could be extremely costly as it would require replacing each and every external device at each and every teller station. In a large retail chain that could add up to hundreds of thousands of devices and millions of dollars. In addition, as USB-based devices are accessed differently than serial devices, it would mean rewriting large amounts of application software in order to get the new system communicating properly.
Using USB to Serial adapters is a far more economical solution. Quatech USB to serial adapters enumerate themselves as standard COM ports compatible with all standard RS-232 devices and the software created for them. This means that users can take advantage of USB technology without replacing a single peripheral device or doing any additional programming. A typical POS station implemented via a USB to serial adapter is shown below.
for more information click >> QSU2-100
or visit Interworld Electronincs