Explanation A USB to 9-pin serial adapter can be used to connect the new computer to the point-of-sale system using a USB port. USB is a common and versatile port type found on most computers. If a technician is replacing a computer with a connected point-of-sale system using a 9-pin serial adapter and the new computer does not have a 9-pin serial port, an adapter can be installed on the USB port in order to connect to the point-of-sale system. A USB-to-serial adapter can be used to connect a serial device to a USB port on a computer.