sentences:  The physical hardware communications link is not defined by SCPI.While it was originally created for the IEEE-488.1 (GPIB) bus, SCPI can also be used with RS-232, RS-422, Ethernet, USB, VXIbus, HiSLIP, etc.SCPI commands are ASCII textual strings, which are sent to the instrument over the physical layer (e.g., IEEE-488.1).