Printronix L5020 - Manual (Page 220)

Appendix Interfaces
222
Printing at full-rated speed may require either an RS-422 or parallel
connection for wide format printing applications.
RS-232 Serial Interface Connector Pin Assignments
The printer provides a 25-pin DB-25S connector inside the lower
cabinet for connection of a serial interface cable. This connector is
also used for the RS-422 serial interface. Selection of the desired
interface is determined by the position of the RS-232/422 switch
located inside the lower cabinet of the printer.
The following table lists the pin assignments of the RS-232
interface connector.
Pin Signal Direction
1 Chassis Ground Not applicable
2 Transmit Data (TxD) From printer
3 Receive Data (RxD) To printer
4 Request To Send (RTS) From printer
5 Clear To Send (CTS) To printer
6 Data Set Ready (DSR) To printer
7 Signal Ground Not applicable
8 Carrier Detect (CD) To printer
11, 14 Reverse Channel (RC) From printer
20 Data Terminal Ready (DTR) From printer