HP QMS 1660 - Manual (Page 231)

Cable Pinouts
B-9 Technical Specifications
RS-422 Serial
This table gives the correct pinouts for the 9-pin male RS-422 serial
interface:
Pin Name Pinout View from Printer Interface
1 Not Used
2 Receive Data (RXD)
3 Transmit Data (TXD)
4 Data Terminal Ready (DTR)
5 Signal Ground (GND)
6 Data Set Ready (DSR)
7 Ready To Send (RTS)
8 Clear To Send (CTS)
9 Reserved