Connect to Asynchronous Serial Diagnostic & Programming Ports with your USB only PC To better support field service pools, we created "LS" versions of these popular converters. Simply put, "LS" stands for "Locked Serial Number." Units that are programmed with the "locked serial number" are field service friendly in that they all share the same serial number. This feature allows for a single driver installation - if you plug another "LS" version of the same model number into your PC, it will be assigned to the same COM port. With the standard version each time you install a product with the same model number, you must go through the driver installation and it will be assigned to a unique COM port.