Strange. Neither mine or Mike's one came with a usb cable, but 2 MAC RS422 to PC RS232 adapter (mini-din 8 pins to sub-D 9 pins ,and sub-D 25 pins). Mike has a serial-usb converter, but from a computer point of view, the DTP92Q is a serial device.
I'm told they do exist, since someone reported that their DTP92Q USB didn't work. There was certainly a DTP41 along similar lines that I saw at one stage, that supported USB or serial. Graeme Gill.