SATO XL400/410 - Manual (Page 173)

Programming Manual 5. Interface Specifications
SATO RISC Printers 173
5 To Printer CTS (Clear to Send) - When this line is high, the printer
assumes that data is ready to be transmitted. The printer
will not receive data when this line is low. If this line is
not being used, it should be tied high (to pin 4).
6 To Printer DSR (Data Set Ready) - When this line is high, the prin-
ter will be ready to receive data. This line must be high
before data is transmitted. If this line is not being used, it
should be tied high (to pin 20).
7 Reference SG (Signal Ground).
20 To Host DTR (Data Terminal Ready) - This signal applies to
Ready/Busy flow control. The printer is ready to receive
data when this pin is high. It goes low when the printer is
off-line, either manually or due to an error condition, and
while printing in the Single Job Buffer mode. It will also
go low when the data in the buffer reaches the Buffer
Near Full level.