Many computers do not have the standard RS-232 COM ports or only a few are available. The USB-to-Serial converter allows the addition of many more COM ports with use of the present USB serial standard. Either a single COM port can be provided with #17690 or up to 4 COM ports can be made available with the #17691.
There is significant variation in the interface protocol of these devices from the multitude of manufactures and chip sets on the market. To insure compatibility, we suggest you acquire these from Optec or inquire with the Optec users group about the compatibility of other models.